fio(1)                      General Commands Manual                     fio(1)

       fio - flexible I/O tester

       fio [options] [jobfile]...

       fio is a tool that will spawn a number of threads or processes doing a
       particular type of I/O action as specified by the user.  The typical
       use of fio is to write a job file matching the I/O load one wants to

              Enable verbose tracing type of various fio actions. May be `all'
              for all types or individual types separated by a comma (e.g.
              `--debug=file,mem' will enable file and memory debugging).
              `help' will list all available tracing options.

              Parse options only, don't start any I/O.

              Write output to filename.

              Set the reporting format to `normal', `terse', `json', or
              `json+'. Multiple formats can be selected, separate by a comma.
              `terse' is a CSV based format. `json+' is like `json', except it
              adds a full dump of the latency buckets.

              Generate aggregate bandwidth logs.

              Print statistics in a terse, semicolon-delimited format.

              Print statistics in selected mode AND terse, semicolon-delimited
              format.  Deprecated, use --output-format instead to select
              multiple formats.

              Set terse version output format (default `3', or `2', `4', `5').

              Print version information and exit.

       --help Print a summary of the command line options and exit.

              Perform test and validation of internal CPU clock.

              Test the speed of the built-in checksumming functions. If no
              argument is given, all of them are tested. Alternatively, a
              comma separated list can be passed, in which case the given ones
              are tested.

              Print help information for command. May be `all' for all

              List all commands defined by ioengine, or print help for command
              defined by ioengine. If no ioengine is given, list all available

              Convert jobfile to a set of command-line options.

              Turn on safety read-only checks, preventing writes. The
              --readonly option is an extra safety guard to prevent users from
              accidentally starting a write workload when that is not desired.
              Fio will only write if `rw=write/randwrite/rw/randrw' is given.
              This extra safety net can be used as an extra precaution as
              --readonly will also enable a write check in the I/O engine core
              to prevent writes due to unknown user space bug(s).

              Specifies when real-time ETA estimate should be printed. when
              may be `always', `never' or `auto'. `auto' is the default, it
              prints ETA when requested if the output is a TTY. `always'
              disregards the output type, and prints ETA when requested.
              `never' never prints ETA.

              By default, fio requests client ETA status roughly every second.
              With this option, the interval is configurable. Fio imposes a
              minimum allowed time to avoid flooding the console, less than
              250 msec is not supported.

              Force a new line for every time period passed. When the unit is
              omitted, the value is interpreted in seconds.

              Force a full status dump of cumulative (from job start) values
              at time intervals. This option does *not* provide per-period
              measurements. So values such as bandwidth are running averages.
              When the time unit is omitted, time is interpreted in seconds.

              Only run specified section name in job file. Multiple sections
              can be specified.  The --section option allows one to combine
              related jobs into one file.  E.g. one job file could define
              light, moderate, and heavy sections. Tell fio to run only the
              "heavy" section by giving `--section=heavy' command line option.
              One can also specify the "write" operations in one section and
              "verify" operation in another section. The --section option only
              applies to job sections. The reserved *global* section is always
              parsed and used.

              Set the internal smalloc pool size to kb in KiB. The
              --alloc-size switch allows one to use a larger pool size for
              smalloc.  If running large jobs with randommap enabled, fio can
              run out of memory.  Smalloc is an internal allocator for shared
              structures from a fixed size memory pool and can grow to 16
              pools. The pool size defaults to 16MiB.  NOTE: While running
              `.fio_smalloc.*' backing store files are visible in `/tmp'.

              All fio parser warnings are fatal, causing fio to exit with an

              Set the maximum number of threads/processes to support to nr.
              NOTE: On Linux, it may be necessary to increase the shared-
              memory limit (`/proc/sys/kernel/shmmax') if fio runs into errors
              while creating jobs.

              Start a backend server, with args specifying what to listen to.
              See CLIENT/SERVER section.

              Background a fio server, writing the pid to the given pidfile

              Instead of running the jobs locally, send and run them on the
              given hostname or set of hostnames. See CLIENT/SERVER section.

              Tell fio server to load this local file.

              Report CPU idleness. option is one of the following:

                            Run unit work calibration only and exit.

                     system Show aggregate system idleness and unit work.

                     percpu As system but also show per CPU idleness.

              Inflate and output compressed log.

              Execute trigger command when file exists.

              Execute trigger at this time.

              Set this command as local trigger.

              Set this command as remote trigger.

              Use this path for fio state generated files.

       Any parameters following the options will be assumed to be job files,
       unless they match a job file parameter. Multiple job files can be
       listed and each job file will be regarded as a separate group. Fio will
       stonewall execution between each group.

       Fio accepts one or more job files describing what it is supposed to do.
       The job file format is the classic ini file, where the names enclosed
       in [] brackets define the job name. You are free to use any ASCII name
       you want, except *global* which has special meaning. Following the job
       name is a sequence of zero or more parameters, one per line, that
       define the behavior of the job. If the first character in a line is a
       ';' or a '#', the entire line is discarded as a comment.

       A *global* section sets defaults for the jobs described in that file. A
       job may override a *global* section parameter, and a job file may even
       have several *global* sections if so desired. A job is only affected by
       a *global* section residing above it.

       The --cmdhelp option also lists all options. If used with an command
       argument, --cmdhelp will detail the given command.

       See the `examples/' directory for inspiration on how to write job
       files. Note the copyright and license requirements currently apply to
       `examples/' files.

       Some parameters take an option of a given type, such as an integer or a
       string. Anywhere a numeric value is required, an arithmetic expression
       may be used, provided it is surrounded by parentheses. Supported
       operators are:

              addition (+)

              subtraction (-)

              multiplication (*)

              division (/)

              modulus (%)

              exponentiation (^)

       For time values in expressions, units are microseconds by default. This
       is different than for time values not in expressions (not enclosed in

       The following parameter types are used.

       str    String. A sequence of alphanumeric characters.

       time   Integer with possible time suffix. Without a unit value is
              interpreted as seconds unless otherwise specified. Accepts a
              suffix of 'd' for days, 'h' for hours, 'm' for minutes, 's' for
              seconds, 'ms' (or 'msec') for milliseconds and 'us' (or 'usec')
              for microseconds. For example, use 10m for 10 minutes.

       int    Integer. A whole number value, which may contain an integer
              prefix and an integer suffix.

                     [*integer prefix*] **number** [*integer suffix*]

              The optional *integer prefix* specifies the number's base. The
              default is decimal. *0x* specifies hexadecimal.

              The optional *integer suffix* specifies the number's units, and
              includes an optional unit prefix and an optional unit. For
              quantities of data, the default unit is bytes. For quantities of
              time, the default unit is seconds unless otherwise specified.

              With `kb_base=1000', fio follows international standards for
              unit prefixes. To specify power-of-10 decimal values defined in
              the International System of Units (SI):

                     K means kilo (K) or 1000
                     M means mega (M) or 1000**2
                     G means giga (G) or 1000**3
                     T means tera (T) or 1000**4
                     P means peta (P) or 1000**5

              To specify power-of-2 binary values defined in IEC 80000-13:

                     Ki means kibi (Ki) or 1024
                     Mi means mebi (Mi) or 1024**2
                     Gi means gibi (Gi) or 1024**3
                     Ti means tebi (Ti) or 1024**4
                     Pi means pebi (Pi) or 1024**5

              With `kb_base=1024' (the default), the unit prefixes are
              opposite from those specified in the SI and IEC 80000-13
              standards to provide compatibility with old scripts. For
              example, 4k means 4096.

              For quantities of data, an optional unit of 'B' may be included
              (e.g., 'kB' is the same as 'k').

              The *integer suffix* is not case sensitive (e.g., m/mi mean
              mebi/mega, not milli). 'b' and 'B' both mean byte, not bit.

              Examples with `kb_base=1000':

                     4 KiB: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
                     1 MiB: 1048576, 1m, 1024k
                     1 MB: 1000000, 1mi, 1000ki
                     1 TiB: 1073741824, 1t, 1024m, 1048576k
                     1 TB: 1000000000, 1ti, 1000mi, 1000000ki

              Examples with `kb_base=1024' (default):

                     4 KiB: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
                     1 MiB: 1048576, 1m, 1024k
                     1 MB: 1000000, 1mi, 1000ki
                     1 TiB: 1073741824, 1t, 1024m, 1048576k
                     1 TB: 1000000000, 1ti, 1000mi, 1000000ki

              To specify times (units are not case sensitive):

                     D means days
                     H means hours
                     M mean minutes
                     s or sec means seconds (default)
                     ms or msec means milliseconds
                     us or usec means microseconds

              If the option accepts an upper and lower range, use a colon ':'
              or minus '-' to separate such values. See irange parameter type.
              If the lower value specified happens to be larger than the upper
              value the two values are swapped.

       bool   Boolean. Usually parsed as an integer, however only defined for
              true and false (1 and 0).

       irange Integer range with suffix. Allows value range to be given, such
              as 1024-4096. A colon may also be used as the separator, e.g.
              1k:4k. If the option allows two sets of ranges, they can be
              specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
              int parameter type.

              A list of floating point numbers, separated by a ':' character.

       With the above in mind, here follows the complete list of fio job

              Select the interpretation of unit prefixes in input parameters.

                     1000   Inputs comply with IEC 80000-13 and the
                            International System of Units (SI). Use:

                            - power-of-2 values with IEC prefixes (e.g., KiB)
                            - power-of-10 values with SI prefixes (e.g., kB)

                     1024   Compatibility mode (default). To avoid breaking
                            old scripts:

                            - power-of-2 values with SI prefixes
                            - power-of-10 values with IEC prefixes

              See bs for more details on input parameters.

              Outputs always use correct prefixes. Most outputs include both
              side-by-side, like:

                     bw=2383.3kB/s (2327.4KiB/s)

              If only one value is reported, then kb_base selects the one to

                     1000 -- SI prefixes
                     1024 -- IEC prefixes

              Base unit for reporting. Allowed values are:

                     0      Use auto-detection (default).

                     8      Byte based.

                     1      Bit based.

   Job description
              ASCII name of the job. This may be used to override the name
              printed by fio for this job. Otherwise the job name is used. On
              the command line this parameter has the special purpose of also
              signaling the start of a new job.

              Text description of the job. Doesn't do anything except dump
              this text description when this job is run. It's not parsed.

              Run the specified number of iterations of this job. Used to
              repeat the same workload a given number of times. Defaults to 1.

              Create the specified number of clones of this job. Each clone of
              job is spawned as an independent thread or process. May be used
              to setup a larger number of threads/processes doing the same
              thing. Each thread is reported separately; to see statistics for
              all clones as a whole, use group_reporting in conjunction with
              new_group.  See --max-jobs. Default: 1.

   Time related parameters
              Tell fio to terminate processing after the specified period of
              time. It can be quite hard to determine for how long a specified
              job will run, so this parameter is handy to cap the total
              runtime to a given time. When the unit is omitted, the value is
              intepreted in seconds.

              If set, fio will run for the duration of the runtime specified
              even if the file(s) are completely read or written. It will
              simply loop over the same workload as many times as the runtime

              Delay the start of job for the specified amount of time. Can be
              a single value or a range. When given as a range, each thread
              will choose a value randomly from within the range. Value is in
              seconds if a unit is omitted.

              If set, fio will run the specified workload for this amount of
              time before logging any performance numbers. Useful for letting
              performance settle before logging results, thus minimizing the
              runtime required for stable results. Note that the ramp_time is
              considered lead in time for a job, thus it will increase the
              total runtime if a special timeout or runtime is specified. When
              the unit is omitted, the value is given in seconds.

              Use the given clocksource as the base of timing. The supported
              options are:



                     cpu    Internal CPU clock source

              cpu is the preferred clocksource if it is reliable, as it is
              very fast (and fio is heavy on time calls). Fio will
              automatically use this clocksource if it's supported and
              considered reliable on the system it is running on, unless
              another clocksource is specifically set. For x86/x86-64 CPUs,
              this means supporting TSC Invariant.

              Enable all of the gettimeofday(2) reducing options
              (disable_clat, disable_slat, disable_bw_measurement) plus reduce
              precision of the timeout somewhat to really shrink the
              gettimeofday(2) call count. With this option enabled, we only do
              about 0.4% of the gettimeofday(2) calls we would have done if
              all time keeping was enabled.

              Sometimes it's cheaper to dedicate a single thread of execution
              to just getting the current time. Fio (and databases, for
              instance) are very intensive on gettimeofday(2) calls. With this
              option, you can set one CPU aside for doing nothing but logging
              current time to a shared memory location. Then the other
              threads/processes that run I/O workloads need only copy that
              segment, instead of entering the kernel with a gettimeofday(2)
              call. The CPU set aside for doing these time calls will be
              excluded from other uses. Fio will manually clear it from the
              CPU mask of other jobs.

   Target file/device
              Prefix filenames with this directory. Used to place files in a
              different location than `./'. You can specify a number of
              directories by separating the names with a ':' character. These
              directories will be assigned equally distributed to job clones
              created by numjobs as long as they are using generated
              filenames. If specific filename(s) are set fio will use the
              first listed directory, and thereby matching the filename
              semantic which generates a file each clone if not specified, but
              let all clones use the same if set.

              See the filename option for information on how to escape ':' and
              '´ characters within the directory path itself.

              Fio normally makes up a filename based on the job name, thread
              number, and file number (see filename_format). If you want to
              share files between threads in a job or several jobs with fixed
              file paths, specify a filename for each of them to override the
              default. If the ioengine is file based, you can specify a number
              of files by separating the names with a ':' colon. So if you
              wanted a job to open `/dev/sda' and `/dev/sdb' as the two
              working files, you would use `filename=/dev/sda:/dev/sdb'. This
              also means that whenever this option is specified, nrfiles is
              ignored. The size of regular files specified by this option will
              be size divided by number of files unless an explicit size is
              specified by filesize.

              Each colon and backslash in the wanted path must be escaped with
              a '´ character. For instance, if the path is
              `/dev/dsk/foo@3,0:c' then you would use
              `filename=/dev/dsk/foo@3,0\:c' and if the path is `F:\\filename'
              then you would use `filename=F\:\\filename'.

              On Windows, disk devices are accessed as `\\\\.\\PhysicalDrive0'
              for the first device, `\\\\.\\PhysicalDrive1' for the second
              etc.  Note: Windows and FreeBSD prevent write access to areas of
              the disk containing in-use data (e.g. filesystems).

              The filename `-' is a reserved name, meaning *stdin* or
              *stdout*. Which of the two depends on the read/write direction

              If sharing multiple files between jobs, it is usually necessary
              to have fio generate the exact names that you want. By default,
              fio will name a file based on the default file format
              specification of `jobname.jobnumber.filenumber'. With this
              option, that can be customized. Fio will recognize and replace
              the following keywords in this string:

                            The name of the worker thread or process.

                            The incremental number of the worker thread or

                            The incremental number of the file for that worker
                            thread or process.

              To have dependent jobs share a set of files, this option can be
              set to have fio generate filenames that are shared between the
              two. For instance, if `testfiles.$filenum' is specified, file
              number 4 for any job will be named `testfiles.4'. The default of
              `$jobname.$jobnum.$filenum' will be used if no other format
              specifier is given.

              If you specify a path then the directories will be created up to
              the main directory for the file.  So for example if you specify
              `a/b/c/$jobnum` then the directories a/b/c will be created
              before the file setup part of the job.  If you specify directory
              then the path will be relative that directory, otherwise it is
              treated as the absolute path.

              To avoid collisions between networked clients, fio defaults to
              prefixing any generated filenames (with a directory specified)
              with the source of the client connecting. To disable this
              behavior, set this option to 0.

              Recursively open any files below directory str.

              Fio defaults to not locking any files before it does I/O to
              them. If a file or file descriptor is shared, fio can serialize
              I/O to that file to make the end result consistent. This is
              usual for emulating real workloads that share files. The lock
              modes are:

                     none   No locking. The default.

                            Only one thread or process may do I/O at a time,
                            excluding all others.

                            Read-write locking on the file. Many readers may
                            access the file at the same time, but writes get
                            exclusive access.

              Number of files to use for this job. Defaults to 1. The size of
              files will be size divided by this unless explicit size is
              specified by filesize. Files are created for each thread
              separately, and each file will have a file number within its
              name by default, as explained in filename section.

              Number of files to keep open at the same time. Defaults to the
              same as nrfiles, can be set smaller to limit the number
              simultaneous opens.

              Defines how fio decides which file from a job to service next.
              The following types are defined:

                     random Choose a file at random.

                            Round robin over opened files. This is the

                            Finish one file before moving on to the next.
                            Multiple files can still be open depending on

                     zipf   Use a Zipf distribution to decide what file to

                     pareto Use a Pareto distribution to decide what file to

                     normal Use a Gaussian (normal) distribution to decide
                            what file to access.

                     gauss  Alias for normal.

              For random, roundrobin, and sequential, a postfix can be
              appended to tell fio how many I/Os to issue before switching to
              a new file. For example, specifying `file_service_type=random:8'
              would cause fio to issue 8 I/Os before selecting a new file at
              random. For the non-uniform distributions, a floating point
              postfix can be given to influence how the distribution is
              skewed. See random_distribution for a description of how that
              would work.

              Attempt to switch the device hosting the file to the specified
              I/O scheduler before running.

              If true, serialize the file creation for the jobs. This may be
              handy to avoid interleaving of data files, which may greatly
              depend on the filesystem used and even the number of processors
              in the system. Default: true.

              fsync(2) the data file after creation. This is the default.

              If true, don't pre-create files but allow the job's open() to
              create a file when it's time to do I/O. Default: false --
              pre-create all necessary files when the job starts.

              If true, fio will only run the setup phase of the job. If files
              need to be laid out or updated on disk, only that will be done
              -- the actual job contents are not executed. Default: false.

              If true, fio is permitted to create files as part of its
              workload. If this option is false, then fio will error out if
              the files it needs to use don't already exist. Default: true.

              If this isn't set, fio will abort jobs that are destructive
              (e.g. that write) to what appears to be a mounted device or
              partition. This should help catch creating inadvertently
              destructive tests, not realizing that the test will destroy data
              on the mounted file system. Note that some platforms don't allow
              writing against a mounted device regardless of this option.
              Default: false.

              If this is given, files will be pre-read into memory before
              starting the given I/O operation. This will also clear the
              invalidate flag, since it is pointless to pre-read and then drop
              the cache. This will only work for I/O engines that are
              seek-able, since they allow you to read the same data multiple
              times. Thus it will not work on non-seekable I/O engines (e.g.
              network, splice). Default: false.

              Unlink the job files when done. Not the default, as repeated
              runs of that job would then waste time recreating the file set
              again and again. Default: false.

              Unlink job files after each iteration or loop. Default: false.

              Divide a file into zones of the specified size. See zoneskip.

              Give size of an I/O zone. See zoneskip.

              Skip the specified number of bytes when zonesize data has been
              read. The two zone options can be used to only do I/O on zones
              of a file.

   I/O type
              If value is true, use non-buffered I/O. This is usually
              O_DIRECT. Note that OpenBSD and ZFS on Solaris don't support
              direct I/O. On Windows the synchronous ioengines don't support
              direct I/O. Default: false.

              If value is true, attempt to use atomic direct I/O. Atomic
              writes are guaranteed to be stable once acknowledged by the
              operating system. Only Linux supports O_ATOMIC right now.

              If value is true, use buffered I/O. This is the opposite of the
              direct option. Defaults to true.

       readwrite=str, rw=str
              Type of I/O pattern. Accepted values are:

                     read   Sequential reads.

                     write  Sequential writes.

                     trim   Sequential trims (Linux block devices only).

                            Random reads.

                            Random writes.

                            Random trims (Linux block devices only).

                            Sequential mixed reads and writes.

                     randrw Random mixed reads and writes.

                            Sequential trim+write sequences. Blocks will be
                            trimmed first, then the same blocks will be
                            written to.

              Fio defaults to read if the option is not specified. For the
              mixed I/O types, the default is to split them 50/50. For certain
              types of I/O the result may still be skewed a bit, since the
              speed may be different.

              It is possible to specify the number of I/Os to do before
              getting a new offset by appending `:<nr>' to the end of the
              string given. For a random read, it would look like
              `rw=randread:8' for passing in an offset modifier with a value
              of 8. If the suffix is used with a sequential I/O pattern, then
              the `<nr>' value specified will be added to the generated offset
              for each I/O turning sequential I/O into sequential I/O with
              holes.  For instance, using `rw=write:4k' will skip 4k for every
              write. Also see the rw_sequencer option.

              If an offset modifier is given by appending a number to the
              `rw=str' line, then this option controls how that number
              modifies the I/O offset being generated. Accepted values are:

                            Generate sequential offset.

                            Generate the same offset.

              sequential is only useful for random I/O, where fio would
              normally generate a new random offset for every I/O. If you
              append e.g. 8 to randread, you would get a new random offset for
              every 8 I/Os. The result would be a seek for only every 8 I/Os,
              instead of for every I/O. Use `rw=randread:8' to specify that.
              As sequential I/O is already sequential, setting sequential for
              that would not result in any differences. identical behaves in a
              similar fashion, except it sends the same offset 8 number of
              times before generating a new offset.

              Fio normally reports statistics on a per data direction basis,
              meaning that reads, writes, and trims are accounted and reported
              separately. If this option is set fio sums the results and
              report them as "mixed" instead.

              Seed the random number generator used for random I/O patterns in
              a predictable way so the pattern is repeatable across runs.
              Default: true.

              Seed all random number generators in a predictable way so
              results are repeatable across runs. Default: false.

              Seed the random number generators based on this seed value, to
              be able to control what sequence of output is being generated.
              If not set, the random sequence depends on the randrepeat

              Whether pre-allocation is performed when laying down files.
              Accepted values are:

                     none   Do not pre-allocate space.

                     native Use a platform's native pre-allocation call but
                            fall back to none behavior if it fails/is not

                     posix  Pre-allocate via posix_fallocate(3).

                     keep   Pre-allocate via fallocate(2) with
                            FALLOC_FL_KEEP_SIZE set.

                     0      Backward-compatible alias for none.

                     1      Backward-compatible alias for posix.

              May not be available on all supported platforms. keep is only
              available on Linux. If using ZFS on Solaris this cannot be set
              to posix because ZFS doesn't support pre-allocation. Default:
              native if any pre-allocation methods are available, none if not.

              Use posix_fadvise(2) or posix_madvise(2) to advise the kernel
              what I/O patterns are likely to be issued. Accepted values are:

                     0      Backwards compatible hint for "no hint".

                     1      Backwards compatible hint for "advise with fio
                            workload type". This uses FADV_RANDOM for a random
                            workload, and FADV_SEQUENTIAL for a sequential

                            Advise using FADV_SEQUENTIAL.

                     random Advise using FADV_RANDOM.

              Use fcntl(2) to advise the kernel what life time to expect from
              a write. Only supported on Linux, as of version 4.13. Accepted
              values are:

                     none   No particular life time associated with this file.

                     short  Data written to this file has a short life time.

                     medium Data written to this file has a medium life time.

                     long   Data written to this file has a long life time.

                            Data written to this file has a very long life

              The values are all relative to each other, and no absolute
              meaning should be associated with them.

              Start I/O at the provided offset in the file, given as either a
              fixed size in bytes or a percentage. If a percentage is given,
              the generated offset will be aligned to the minimum blocksize or
              to the value of offset_align if provided. Data before the given
              offset will not be touched. This effectively caps the file size
              at `real_size - offset'. Can be combined with size to constrain
              the start and end range of the I/O workload.  A percentage can
              be specified by a number between 1 and 100 followed by '%', for
              example, `offset=20%' to specify 20%.

              If set to non-zero value, the byte offset generated by a
              percentage offset is aligned upwards to this value. Defaults to
              0 meaning that a percentage offset is aligned to the minimum
              block size.

              If this is provided, then the real offset becomes `offset +
              offset_increment * thread_number', where the thread number is a
              counter that starts at 0 and is incremented for each sub-job
              (i.e. when numjobs option is specified). This option is useful
              if there are several jobs which are intended to operate on a
              file in parallel disjoint segments, with even spacing between
              the starting points.

              Fio will normally perform I/Os until it has exhausted the size
              of the region set by size, or if it exhaust the allocated time
              (or hits an error condition). With this setting, the range/size
              can be set independently of the number of I/Os to perform. When
              fio reaches this number, it will exit normally and report
              status. Note that this does not extend the amount of I/O that
              will be done, it will only stop fio if this condition is met
              before other end-of-job criteria.

              If writing to a file, issue an fsync(2) (or its equivalent) of
              the dirty data for every number of blocks given. For example, if
              you give 32 as a parameter, fio will sync the file after every
              32 writes issued. If fio is using non-buffered I/O, we may not
              sync the file. The exception is the sg I/O engine, which
              synchronizes the disk cache anyway. Defaults to 0, which means
              fio does not periodically issue and wait for a sync to complete.
              Also see end_fsync and fsync_on_close.

              Like fsync but uses fdatasync(2) to only sync data and not
              metadata blocks. In Windows, FreeBSD, and DragonFlyBSD there is
              no fdatasync(2) so this falls back to using fsync(2).  Defaults
              to 0, which means fio does not periodically issue and wait for a
              data-only sync to complete.

              Make every N-th write a barrier write.

              Use sync_file_range(2) for every int number of write operations.
              Fio will track range of writes that have happened since the last
              sync_file_range(2) call. str can currently be one or more of:


                     write  SYNC_FILE_RANGE_WRITE


              So if you do `sync_file_range=wait_before,write:8', fio would
              every 8 writes. Also see the sync_file_range(2) man page. This
              option is Linux specific.

              If true, writes to a file will always overwrite existing data.
              If the file doesn't already exist, it will be created before the
              write phase begins. If the file exists and is large enough for
              the specified write phase, nothing will be done. Default: false.

              If true, fsync(2) file contents when a write stage has
              completed.  Default: false.

              If true, fio will fsync(2) a dirty file on close. This differs
              from end_fsync in that it will happen on every file close, not
              just at the end of the job. Default: false.

              Percentage of a mixed workload that should be reads. Default:

              Percentage of a mixed workload that should be writes. If both
              rwmixread and rwmixwrite is given and the values do not add up
              to 100%, the latter of the two will be used to override the
              first. This may interfere with a given rate setting, if fio is
              asked to limit reads or writes to a certain rate. If that is the
              case, then the distribution may be skewed. Default: 50.

              By default, fio will use a completely uniform random
              distribution when asked to perform random I/O. Sometimes it is
              useful to skew the distribution in specific ways, ensuring that
              some parts of the data is more hot than others.  fio includes
              the following distribution models:

                     random Uniform random distribution

                     zipf   Zipf distribution

                     pareto Pareto distribution

                     normal Normal (Gaussian) distribution

                     zoned  Zoned random distribution zoned_abs Zoned absolute
                            random distribution

              When using a zipf or pareto distribution, an input value is also
              needed to define the access pattern. For zipf, this is the `Zipf
              theta'.  For pareto, it's the `Pareto power'. Fio includes a
              test program, fio-genzipf, that can be used visualize what the
              given input values will yield in terms of hit rates. If you
              wanted to use zipf with a `theta' of 1.2, you would use
              `random_distribution=zipf:1.2' as the option. If a non-uniform
              model is used, fio will disable use of the random map. For the
              normal distribution, a normal (Gaussian) deviation is supplied
              as a value between 0 and 100.

              For a zoned distribution, fio supports specifying percentages of
              I/O access that should fall within what range of the file or
              device. For example, given a criteria of:

                     60% of accesses should be to the first 10%
                     30% of accesses should be to the next 20%
                     8% of accesses should be to the next 30%
                     2% of accesses should be to the next 40%

              we can define that through zoning of the random accesses. For
              the above example, the user would do:


              A zoned_abs distribution works exactly like thezoned, except
              that it takes absolute sizes. For example, let's say you wanted
              to define access according to the following criteria:

                     60% of accesses should be to the first 20G
                     30% of accesses should be to the next 100G
                     10% of accesses should be to the next 500G

              we can define an absolute zoning distribution with:


              For both zoned and zoned_abs, fio supports defining up to 256
              separate zones.

              Similarly to how bssplit works for setting ranges and
              percentages of block sizes. Like bssplit, it's possible to
              specify separate zones for reads, writes, and trims. If just one
              set is given, it'll apply to all of them.

              For a random workload, set how big a percentage should be
              random. This defaults to 100%, in which case the workload is
              fully random. It can be set from anywhere from 0 to 100. Setting
              it to 0 would make the workload fully sequential. Any setting in
              between will result in a random mix of sequential and random
              I/O, at the given percentages. Comma-separated values may be
              specified for reads, writes, and trims as described in

              Normally fio will cover every block of the file when doing
              random I/O. If this option is given, fio will just get a new
              random offset without looking at past I/O history. This means
              that some blocks may not be read or written, and that some
              blocks may be read/written more than once. If this option is
              used with verify and multiple blocksizes (via bsrange), only
              intact blocks are verified, i.e., partially-overwritten blocks
              are ignored.

              See norandommap. If fio runs with the random block map enabled
              and it fails to allocate the map, if this option is set it will
              continue without a random block map. As coverage will not be as
              complete as with random maps, this option is disabled by

              Fio supports the following engines for generating I/O offsets
              for random I/O:

                            Strong 2^88 cycle random number generator.

                     lfsr   Linear feedback shift register generator.

                            Strong 64-bit 2^258 cycle random number generator.

              tausworthe is a strong random number generator, but it requires
              tracking on the side if we want to ensure that blocks are only
              read or written once. lfsr guarantees that we never generate the
              same offset twice, and it's also less computationally expensive.
              It's not a true random generator, however, though for I/O
              purposes it's typically good enough. lfsr only works with single
              block sizes, not with workloads that use multiple block sizes.
              If used with such a workload, fio may read or write some blocks
              multiple times. The default value is tausworthe, unless the
              required space exceeds 2^32 blocks. If it does, then
              tausworthe64 is selected automatically.

   Block size
       blocksize=int[,int][,int], bs=int[,int][,int]
              The block size in bytes used for I/O units. Default: 4096. A
              single value applies to reads, writes, and trims.
              Comma-separated values may be specified for reads, writes, and
              trims. A value not terminated in a comma applies to subsequent
              types. Examples:

                     bs=256k        means 256k for reads, writes and trims.
                     bs=8k,32k      means 8k for reads, 32k for writes and
                     bs=8k,32k,     means 8k for reads, 32k for writes, and
                     default for trims.
                     bs=,8k         means default for reads, 8k for writes and
                     bs=,8k,        means default for reads, 8k for writes,
                     and default for trims.

              A range of block sizes in bytes for I/O units. The issued I/O
              unit will always be a multiple of the minimum size, unless
              blocksize_unaligned is set.  Comma-separated ranges may be
              specified for reads, writes, and trims as described in
              blocksize. Example:


              Sometimes you want even finer grained control of the block sizes
              issued, not just an even split between them. This option allows
              you to weight various block sizes, so that you are able to
              define a specific amount of block sizes issued. The format for
              this option is:


              for as many block sizes as needed. So if you want to define a
              workload that has 50% 64k blocks, 10% 4k blocks, and 40% 32k
              blocks, you would write:


              Ordering does not matter. If the percentage is left blank, fio
              will fill in the remaining values evenly. So a bssplit option
              like this one:


              would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
              always add up to 100, if bssplit is given a range that adds up
              to more, it will error out.

              Comma-separated values may be specified for reads, writes, and
              trims as described in blocksize.

              If you want a workload that has 50% 2k reads and 50% 4k reads,
              while having 90% 4k writes and 10% 8k writes, you would specify:


              Fio supports defining up to 64 different weights for each data

       blocksize_unaligned, bs_unaligned
              If set, fio will issue I/O units with any size within
              blocksize_range, not just multiples of the minimum size. This
              typically won't work with direct I/O, as that normally requires
              sector alignment.

              If this option is set, fio will use the normal read,write
              blocksize settings as sequential,random blocksize settings
              instead. Any random read or write will use the WRITE blocksize
              settings, and any sequential read or write will use the READ
              blocksize settings.

       blockalign=int[,int][,int], ba=int[,int][,int]
              Boundary to which fio will align random I/O units. Default:
              blocksize. Minimum alignment is typically 512b for using direct
              I/O, though it usually depends on the hardware block size. This
              option is mutually exclusive with using a random map for files,
              so it will turn off that option. Comma-separated values may be
              specified for reads, writes, and trims as described in

   Buffers and memory
              Initialize buffers with all zeros. Default: fill buffers with
              random data.

              If this option is given, fio will refill the I/O buffers on
              every submit. The default is to only fill it at init time and
              reuse that data. Only makes sense if zero_buffers isn't
              specified, naturally. If data verification is enabled,
              refill_buffers is also automatically enabled.

              If refill_buffers is too costly and the target is using data
              deduplication, then setting this option will slightly modify the
              I/O buffer contents to defeat normal de-dupe attempts. This is
              not enough to defeat more clever block compression attempts, but
              it will stop naive dedupe of blocks. Default: true.

              If this is set, then fio will attempt to provide I/O buffer
              content (on WRITEs) that compresses to the specified level. Fio
              does this by providing a mix of random data followed by fixed
              pattern data. The fixed pattern is either zeros, or the pattern
              specified by buffer_pattern. If the buffer_pattern option is
              used, it might skew the compression ratio slightly. Setting
              buffer_compress_percentage to a value other than 100 will also
              enable refill_buffers in order to reduce the likelihood that
              adjacent blocks are so similar that they over compress when seen
              together. See buffer_compress_chunk for how to set a finer or
              coarser granularity of the random/fixed data regions. Defaults
              to unset i.e., buffer data will not adhere to any compression

              This setting allows fio to manage how big the random/fixed data
              region is when using buffer_compress_percentage. When
              buffer_compress_chunk is set to some non-zero value smaller than
              the block size, fio can repeat the random/fixed region
              throughout the I/O buffer at the specified interval (which
              particularly useful when bigger block sizes are used for a job).
              When set to 0, fio will use a chunk size that matches the block
              size resulting in a single random/fixed region within the I/O
              buffer. Defaults to 512. When the unit is omitted, the value is
              interpreted in bytes.

              If set, fio will fill the I/O buffers with this pattern or with
              the contents of a file. If not set, the contents of I/O buffers
              are defined by the other options related to buffer contents. The
              setting can be any pattern of bytes, and can be prefixed with 0x
              for hex values. It may also be a string, where the string must
              then be wrapped with "". Or it may also be a filename, where the
              filename must be wrapped with '' in which case the file is
              opened and read. Note that not all the file contents will be
              read if that would cause the buffers to overflow. So, for


              Also you can combine everything together in any order:


              If set, fio will generate this percentage of identical buffers
              when writing. These buffers will be naturally dedupable. The
              contents of the buffers depend on what other buffer compression
              settings have been set. It's possible to have the individual
              buffers either fully compressible, or not at all -- this option
              only controls the distribution of unique buffers. Setting this
              option will also enable refill_buffers to prevent every buffer
              being identical.

              Invalidate the buffer/page cache parts of the files to be used
              prior to starting I/O if the platform and file type support it.
              Defaults to true.  This will be ignored if pre_read is also
              specified for the same job.

              Use synchronous I/O for buffered writes. For the majority of I/O
              engines, this means using O_SYNC. Default: false.

       iomem=str, mem=str
              Fio can use various types of memory as the I/O unit buffer. The
              allowed values are:

                     malloc Use memory from malloc(3) as the buffers. Default
                            memory type.

                     shm    Use shared memory as the buffers. Allocated
                            through shmget(2).

                            Same as shm, but use huge pages as backing.

                     mmap   Use mmap(2) to allocate buffers. May either be
                            anonymous memory, or can be file backed if a
                            filename is given after the option. The format is

                            Use a memory mapped huge file as the buffer
                            backing. Append filename after mmaphuge, ala

                            Same as mmap, but use a MMAP_SHARED mapping.

                            Use GPU memory as the buffers for GPUDirect RDMA
                            benchmark.  The ioengine must be rdma.

              The area allocated is a function of the maximum allowed bs size
              for the job, multiplied by the I/O depth given. Note that for
              shmhuge and mmaphuge to work, the system must have free huge
              pages allocated. This can normally be checked and set by
              reading/writing `/proc/sys/vm/nr_hugepages' on a Linux system.
              Fio assumes a huge page is 4MiB in size. So to calculate the
              number of huge pages you need for a given job file, add up the
              I/O depth of all jobs (normally one unless iodepth is used) and
              multiply by the maximum bs set. Then divide that number by the
              huge page size. You can see the size of the huge pages in
              `/proc/meminfo'. If no huge pages are allocated by having a
              non-zero number in `nr_hugepages', using mmaphuge or shmhuge
              will fail. Also see hugepage-size.

              mmaphuge also needs to have hugetlbfs mounted and the file
              location should point there. So if it's mounted in `/huge', you
              would use `mem=mmaphuge:/huge/somefile'.

       iomem_align=int, mem_align=int
              This indicates the memory alignment of the I/O memory buffers.
              Note that the given alignment is applied to the first I/O unit
              buffer, if using iodepth the alignment of the following buffers
              are given by the bs used. In other words, if using a bs that is
              a multiple of the page sized in the system, all buffers will be
              aligned to this value. If using a bs that is not page aligned,
              the alignment of subsequent I/O memory buffers is the sum of the
              iomem_align and bs used.

              Defines the size of a huge page. Must at least be equal to the
              system setting, see `/proc/meminfo'. Defaults to 4MiB. Should
              probably always be a multiple of megabytes, so using
              `hugepage-size=Xm' is the preferred way to set this to avoid
              setting a non-pow-2 bad value.

              Pin the specified amount of memory with mlock(2). Can be used to
              simulate a smaller amount of memory. The amount specified is per

   I/O size
              The total size of file I/O for each thread of this job. Fio will
              run until this many bytes has been transferred, unless runtime
              is limited by other options (such as runtime, for instance, or
              increased/decreased by io_size).  Fio will divide this size
              between the available files determined by options such as
              nrfiles, filename, unless filesize is specified by the job. If
              the result of division happens to be 0, the size is set to the
              physical size of the given files or devices if they exist.  If
              this option is not specified, fio will use the full size of the
              given files or devices. If the files do not exist, size must be
              given. It is also possible to give size as a percentage between
              1 and 100. If `size=20%' is given, fio will use 20% of the full
              size of the given files or devices.  Can be combined with offset
              to constrain the start and end range that I/O will be done

       io_size=int, io_limit=int
              Normally fio operates within the region set by size, which means
              that the size option sets both the region and size of I/O to be
              performed. Sometimes that is not what you want. With this
              option, it is possible to define just the amount of I/O that fio
              should do. For instance, if size is set to 20GiB and io_size is
              set to 5GiB, fio will perform I/O within the first 20GiB but
              exit when 5GiB have been done. The opposite is also possible --
              if size is set to 20GiB, and io_size is set to 40GiB, then fio
              will do 40GiB of I/O within the 0..20GiB region.

              Individual file sizes. May be a range, in which case fio will
              select sizes for files at random within the given range and
              limited to size in total (if that is given). If not given, each
              created file is the same size.  This option overrides size in
              terms of file size, which means this value is used as a fixed
              size or possible range of each file.

              Perform I/O after the end of the file. Normally fio will operate
              within the size of a file. If this option is set, then fio will
              append to the file instead. This has identical behavior to
              setting offset to the size of a file. This option is ignored on
              non-regular files.

       fill_device=bool, fill_fs=bool
              Sets size to something really large and waits for ENOSPC (no
              space left on device) as the terminating condition. Only makes
              sense with sequential write. For a read workload, the mount
              point will be filled first then I/O started on the result. This
              option doesn't make sense if operating on a raw device node,
              since the size of that is already known by the file system.
              Additionally, writing beyond end-of-device will not return
              ENOSPC there.

   I/O engine
              Defines how the job issues I/O to the file. The following types
              are defined:

                     sync   Basic read(2) or write(2) I/O. lseek(2) is used to
                            position the I/O location.  See fsync and
                            fdatasync for syncing write I/Os.

                     psync  Basic pread(2) or pwrite(2) I/O. Default on all
                            supported operating systems except for Windows.

                     vsync  Basic readv(2) or writev(2) I/O. Will emulate
                            queuing by coalescing adjacent I/Os into a single

                     pvsync Basic preadv(2) or pwritev(2) I/O.

                            Basic preadv2(2) or pwritev2(2) I/O.

                     libaio Linux native asynchronous I/O. Note that Linux may
                            only support queued behavior with non-buffered I/O
                            (set `direct=1' or `buffered=0').  This engine
                            defines engine specific options.

                            POSIX asynchronous I/O using aio_read(3) and

                            Solaris native asynchronous I/O.

                            Windows native asynchronous I/O. Default on

                     mmap   File is memory mapped with mmap(2) and data copied
                            to/from using memcpy(3).

                     splice splice(2) is used to transfer the data and
                            vmsplice(2) to transfer data from user space to
                            the kernel.

                     sg     SCSI generic sg v3 I/O. May either be synchronous
                            using the SG_IO ioctl, or if the target is an sg
                            character device we use read(2) and write(2) for
                            asynchronous I/O. Requires filename option to
                            specify either block or character devices.

                     null   Doesn't transfer any data, just pretends to. This
                            is mainly used to exercise fio itself and for
                            debugging/testing purposes.

                     net    Transfer over the network to given `host:port'.
                            Depending on the protocol used, the hostname,
                            port, listen and filename options are used to
                            specify what sort of connection to make, while the
                            protocol option determines which protocol will be
                            used. This engine defines engine specific options.

                            Like net, but uses splice(2) and vmsplice(2) to
                            map data and send/receive.  This engine defines
                            engine specific options.

                     cpuio  Doesn't transfer any data, but burns CPU cycles
                            according to the cpuload and cpuchunks options.
                            Setting cpuload=85 will cause that job to do
                            nothing but burn 85% of the CPU. In case of SMP
                            machines, use `numjobs=<nr_of_cpu>' to get desired
                            CPU usage, as the cpuload only loads a single CPU
                            at the desired rate. A job never finishes unless
                            there is at least one non-cpuio job.

                     guasi  The GUASI I/O engine is the Generic Userspace
                            Asyncronous Syscall Interface approach to async
                            I/O. See
                            for more info on GUASI.

                     rdma   The RDMA I/O engine supports both RDMA memory
                            semantics (RDMA_WRITE/RDMA_READ) and channel
                            semantics (Send/Recv) for the InfiniBand, RoCE and
                            iWARP protocols. This engine defines engine
                            specific options.

                     falloc I/O engine that does regular fallocate to simulate
                            data transfer as fio ioengine.

                            DDIR_READ      does fallocate(,mode =
                            DIR_WRITE      does fallocate(,mode = 0).
                            DDIR_TRIM      does fallocate(,mode =

                            I/O engine that sends ftruncate(2) operations in
                            response to write (DDIR_WRITE) events. Each
                            ftruncate issued sets the file's size to the
                            current block offset. blocksize is ignored.

                            I/O engine that does regular EXT4_IOC_MOVE_EXT
                            ioctls to simulate defragment activity in request
                            to DDIR_WRITE event.

                     rbd    I/O engine supporting direct access to Ceph Rados
                            Block Devices (RBD) via librbd without the need to
                            use the kernel rbd driver. This ioengine defines
                            engine specific options.

                     gfapi  Using GlusterFS libgfapi sync interface to direct
                            access to GlusterFS volumes without having to go
                            through FUSE. This ioengine defines engine
                            specific options.

                            Using GlusterFS libgfapi async interface to direct
                            access to GlusterFS volumes without having to go
                            through FUSE. This ioengine defines engine
                            specific options.

                            Read and write through Hadoop (HDFS). The filename
                            option is used to specify host,port of the hdfs
                            name-node to connect. This engine interprets
                            offsets a little differently. In HDFS, files once
                            created cannot be modified so random writes are
                            not possible. To imitate this the libhdfs engine
                            expects a bunch of small files to be created over
                            HDFS and will randomly pick a file from them based
                            on the offset generated by fio backend (see the
                            example job file to create such files, use
                            `rw=write' option). Please note, it may be
                            necessary to set environment variables to work
                            with HDFS/libhdfs properly. Each job uses its own
                            connection to HDFS.

                     mtd    Read, write and erase an MTD character device
                            (e.g., `/dev/mtd0'). Discards are treated as
                            erases. Depending on the underlying device type,
                            the I/O may have to go in a certain pattern, e.g.,
                            on NAND, writing sequentially to erase blocks and
                            discarding before overwriting. The trimwrite mode
                            works well for this constraint.

                            Read and write using filesystem DAX to a file on a
                            filesystem mounted with DAX on a persistent memory
                            device through the NVML libpmemblk library.

                            Read and write using device DAX to a persistent
                            memory device (e.g., /dev/dax0.0) through the NVML
                            libpmem library.

                            Prefix to specify loading an external I/O engine
                            object file. Append the engine filename, e.g.
                            `ioengine=external:/tmp/foo.o' to load ioengine
                            `foo.o' in `/tmp'. The path can be either absolute
                            or relative. See `engines/skeleton_external.c' in
                            the fio source for details of writing an external
                            I/O engine.

                            Simply create the files and do no I/O to them.
                            You still need to set filesize so that all the
                            accounting still occurs, but no actual I/O will be
                            done other than creating the file.

                            Read and write using mmap I/O to a file on a
                            filesystem mounted with DAX on a persistent memory
                            device through the NVML libpmem library.

   I/O engine specific parameters
       In addition, there are some parameters which are only valid when a
       specific ioengine is in use. These are used identically to normal
       parameters, with the caveat that when used on the command line, they
       must come after the ioengine that defines them is selected.

              Normally, with the libaio engine in use, fio will use the
              io_getevents(3) system call to reap newly returned events. With
              this flag turned on, the AIO ring will be read directly from
              user-space to reap events. The reaping mode is only enabled when
              polling for a minimum of 0 events (e.g. when

              Set RWF_HIPRI on I/O, indicating to the kernel that it's of
              higher priority than normal.

              When hipri is set this determines the probability of a pvsync2
              I/O being high priority. The default is 100%.

              Attempt to use the specified percentage of CPU cycles. This is a
              mandatory option when using cpuio I/O engine.

              Split the load into cycles of the given time. In microseconds.

              Detect when I/O threads are done, then exit.

              The hostname or IP address of a HDFS cluster namenode to

              The listening port of the HFDS cluster namenode.

              The TCP or UDP port to bind to or connect to. If this is used
              with numjobs to spawn multiple instances of the same job type,
              then this will be the starting port number since fio will use a
              range of ports.

              The port to use for RDMA-CM communication. This should be the
              same value on the client and the server side.

              The hostname or IP address to use for TCP, UDP or RDMA-CM based
              I/O.  If the job is a TCP listener or UDP reader, the hostname
              is not used and must be omitted unless it is a valid UDP
              multicast address.

              The IP address of the network interface used to send or receive
              UDP multicast.

              Time-to-live value for outgoing UDP multicast packets. Default:

              Set TCP_NODELAY on TCP connections.

       (netsplice,net)protocol=str, proto=str
              The network protocol to use. Accepted values are:

                     tcp    Transmission control protocol.

                     tcpv6  Transmission control protocol V6.

                     udp    User datagram protocol.

                     udpv6  User datagram protocol V6.

                     unix   UNIX domain socket.

              When the protocol is TCP or UDP, the port must also be given, as
              well as the hostname if the job is a TCP listener or UDP reader.
              For unix sockets, the normal filename option should be used and
              the port is invalid.

              For TCP network connections, tell fio to listen for incoming
              connections rather than initiating an outgoing connection. The
              hostname must be omitted if this option is used.

              Normally a network writer will just continue writing data, and a
              network reader will just consume packages. If `pingpong=1' is
              set, a writer will send its normal payload to the reader, then
              wait for the reader to send the same payload back. This allows
              fio to measure network latencies. The submission and completion
              latencies then measure local time spent sending or receiving,
              and the completion latency measures how long it took for the
              other end to receive and send back. For UDP multicast traffic
              `pingpong=1' should only be set for a single reader when
              multiple readers are listening to the same address.

              Set the desired socket buffer size for the connection.

              Set the TCP maximum segment size (TCP_MAXSEG).

              File will be used as a block donor (swap extents between files).

              Configure donor file blocks allocation strategy:

                     0      Default. Preallocate donor's file on init.

                     1      Allocate space immediately inside defragment
                            event, and free right after event.

              Specifies the name of the Ceph cluster.

              Specifies the name of the RBD.

              Specifies the name of the Ceph pool containing RBD.

              Specifies the username (without the 'client.' prefix) used to
              access the Ceph cluster. If the clustername is specified, the
              clientname shall be the full ** string. If no type.
              prefix is given, fio will add 'client.'  by default.

              Skip operations against known bad blocks.

              libhdfs will create chunk in this HDFS directory.

              The size of the chunk to use for each file.

              The RDMA verb to use on this side of the RDMA ioengine
              connection. Valid values are write, read, send and recv. These
              correspond to the equivalent RDMA verbs (e.g. write = rdma_write
              etc.). Note that this only needs to be specified on the client
              side of the connection. See the examples folder.

              The name to use to bind the local RDMA-CM connection to a local
              RDMA device. This could be a hostname or an IPv4 or IPv6
              address. On the server side this will be passed into the
              rdma_bind_addr() function and on the client site it will be used
              in the rdma_resolve_add() function. This can be useful when
              multiple paths exist between the client and the server or in
              certain loopback configurations.

   I/O depth
              Number of I/O units to keep in flight against the file. Note
              that increasing iodepth beyond 1 will not affect synchronous
              ioengines (except for small degrees when verify_async is in
              use). Even async engines may impose OS restrictions causing the
              desired depth not to be achieved. This may happen on Linux when
              using libaio and not setting `direct=1', since buffered I/O is
              not async on that OS. Keep an eye on the I/O depth distribution
              in the fio output to verify that the achieved depth is as
              expected. Default: 1.

       iodepth_batch_submit=int, iodepth_batch=int
              This defines how many pieces of I/O to submit at once. It
              defaults to 1 which means that we submit each I/O as soon as it
              is available, but can be raised to submit bigger batches of I/O
              at the time. If it is set to 0 the iodepth value will be used.

       iodepth_batch_complete_min=int, iodepth_batch_complete=int
              This defines how many pieces of I/O to retrieve at once. It
              defaults to 1 which means that we'll ask for a minimum of 1 I/O
              in the retrieval process from the kernel. The I/O retrieval will
              go on until we hit the limit set by iodepth_low. If this
              variable is set to 0, then fio will always check for completed
              events before queuing more I/O. This helps reduce I/O latency,
              at the cost of more retrieval system calls.

              This defines maximum pieces of I/O to retrieve at once. This
              variable should be used along with
              iodepth_batch_complete_min=int variable, specifying the range of
              min and max amount of I/O which should be retrieved. By default
              it is equal to iodepth_batch_complete_min value. Example #1:


              which means that we will retrieve at least 1 I/O and up to the
              whole submitted queue depth. If none of I/O has been completed
              yet, we will wait.  Example #2:


              which means that we can retrieve up to the whole submitted queue
              depth, but if none of I/O has been completed yet, we will NOT
              wait and immediately exit the system call. In this example we
              simply do polling.

              The low water mark indicating when to start filling the queue
              again. Defaults to the same as iodepth, meaning that fio will
              attempt to keep the queue full at all times. If iodepth is set
              to e.g. 16 and iodepth_low is set to 4, then after fio has
              filled the queue of 16 requests, it will let the depth drain
              down to 4 before starting to fill it again.

              Serialize in-flight I/Os that might otherwise cause or suffer
              from data races.  When two or more I/Os are submitted
              simultaneously, there is no guarantee that the I/Os will be
              processed or completed in the submitted order. Further, if two
              or more of those I/Os are writes, any overlapping region between
              them can become indeterminate/undefined on certain storage.
              These issues can cause verification to fail erratically when at
              least one of the racing I/Os is changing data and the
              overlapping region has a non-zero size. Setting
              serialize_overlap tells fio to avoid provoking this behavior by
              explicitly serializing in-flight I/Os that have a non-zero
              overlap. Note that setting this option can reduce both
              performance and the iodepth achieved.  Additionally this option
              does not work when io_submit_mode is set to offload. Default:

              This option controls how fio submits the I/O to the I/O engine.
              The default is `inline', which means that the fio job threads
              submit and reap I/O directly. If set to `offload', the job
              threads will offload I/O submission to a dedicated pool of I/O
              threads. This requires some coordination and thus has a bit of
              extra overhead, especially for lower queue depth I/O where it
              can increase latencies. The benefit is that fio can manage
              submission rates independently of the device completion rates.
              This avoids skewed latency reporting if I/O gets backed up on
              the device side (the coordinated omission problem).

   I/O rate
              Stall the job for the specified period of time after an I/O has
              completed before issuing the next. May be used to simulate
              processing being done by an application.  When the unit is
              omitted, the value is interpreted in microseconds. See
              thinktime_blocks and thinktime_spin.

              Only valid if thinktime is set - pretend to spend CPU time doing
              something with the data received, before falling back to
              sleeping for the rest of the period specified by thinktime. When
              the unit is omitted, the value is interpreted in microseconds.

              Only valid if thinktime is set - control how many blocks to
              issue, before waiting thinktime usecs. If not set, defaults to 1
              which will make fio wait thinktime usecs after every block. This
              effectively makes any queue depth setting redundant, since no
              more than 1 I/O will be queued before we have to complete it and
              do our thinktime. In other words, this setting effectively caps
              the queue depth if the latter is larger.

              Cap the bandwidth used by this job. The number is in bytes/sec,
              the normal suffix rules apply. Comma-separated values may be
              specified for reads, writes, and trims as described in

              For example, using `rate=1m,500k' would limit reads to 1MiB/sec
              and writes to 500KiB/sec. Capping only reads or writes can be
              done with `rate=,500k' or `rate=500k,' where the former will
              only limit writes (to 500KiB/sec) and the latter will only limit

              Tell fio to do whatever it can to maintain at least this
              bandwidth. Failing to meet this requirement will cause the job
              to exit. Comma-separated values may be specified for reads,
              writes, and trims as described in blocksize.

              Cap the bandwidth to this number of IOPS. Basically the same as
              rate, just specified independently of bandwidth. If the job is
              given a block size range instead of a fixed value, the smallest
              block size is used as the metric. Comma-separated values may be
              specified for reads, writes, and trims as described in

              If fio doesn't meet this rate of I/O, it will cause the job to
              exit.  Comma-separated values may be specified for reads,
              writes, and trims as described in blocksize.

              This option controls how fio manages rated I/O submissions. The
              default is `linear', which submits I/O in a linear fashion with
              fixed delays between I/Os that gets adjusted based on I/O
              completion rates. If this is set to `poisson', fio will submit
              I/O based on a more real world random request flow, known as the
              Poisson process
              ( The
              lambda will be 10^6 / IOPS for the given workload.

              By default, fio will attempt to catch up to the specified rate
              setting, if any kind of thinktime setting was used. If this
              option is set, then fio will ignore the thinktime and continue
              doing IO at the specified rate, instead of entering a catch-up
              mode after thinktime is done.

   I/O latency
              If set, fio will attempt to find the max performance point that
              the given workload will run at while maintaining a latency below
              this target. When the unit is omitted, the value is interpreted
              in microseconds. See latency_window and latency_percentile.

              Used with latency_target to specify the sample window that the
              job is run at varying queue depths to test the performance. When
              the unit is omitted, the value is interpreted in microseconds.

              The percentage of I/Os that must fall within the criteria
              specified by latency_target and latency_window. If not set, this
              defaults to 100.0, meaning that all I/Os must be equal or below
              to the value set by latency_target.

              If set, fio will exit the job with an ETIMEDOUT error if it
              exceeds this maximum latency. When the unit is omitted, the
              value is interpreted in microseconds.

              Average bandwidth for rate and rate_min over this number of
              milliseconds. Defaults to 1000.

   I/O replay
              Write the issued I/O patterns to the specified file. See
              read_iolog. Specify a separate file for each job, otherwise the
              iologs will be interspersed and the file may be corrupt.

              Open an iolog with the specified filename and replay the I/O
              patterns it contains. This can be used to store a workload and
              replay it sometime later. The iolog given may also be a blktrace
              binary file, which allows fio to replay a workload captured by
              blktrace. See blktrace(8) for how to capture such logging data.
              For blktrace replay, the file needs to be turned into a blkparse
              binary data file first (`blkparse <device> -o /dev/null -d

              When replaying I/O with read_iolog the default behavior is to
              attempt to respect the timestamps within the log and replay them
              with the appropriate delay between IOPS. By setting this
              variable fio will not respect the timestamps and attempt to
              replay them as fast as possible while still respecting ordering.
              The result is the same I/O pattern to a given device, but
              different timings.

              While replaying I/O patterns using read_iolog the default
              behavior is to replay the IOPS onto the major/minor device that
              each IOP was recorded from. This is sometimes undesirable
              because on a different machine those major/minor numbers can map
              to a different device. Changing hardware on the same system can
              also result in a different major/minor mapping.  replay_redirect
              causes all I/Os to be replayed onto the single specified device
              regardless of the device it was recorded from. i.e.
              `replay_redirect=/dev/sdc' would cause all I/O in the blktrace
              or iolog to be replayed onto `/dev/sdc'. This means multiple
              devices will be replayed onto a single device, if the trace
              contains multiple devices. If you want multiple devices to be
              replayed concurrently to multiple redirected devices you must
              blkparse your trace into separate traces and replay them with
              independent fio invocations.  Unfortunately this also breaks the
              strict time ordering between multiple device accesses.

              Force alignment of I/O offsets and lengths in a trace to this
              power of 2 value.

              Scale sector offsets down by this factor when replaying traces.

   Threads, processes and job synchronization
       thread Fio defaults to creating jobs by using fork, however if this
              option is given, fio will create jobs by using POSIX Threads'
              function pthread_create(3) to create threads instead.

              If set, the current job won't be started until all workers of
              the specified waitee job are done.  wait_for operates on the job
              name basis, so there are a few limitations. First, the waitee
              must be defined prior to the waiter job (meaning no forward
              references). Second, if a job is being referenced as a waitee,
              it must have a unique name (no duplicate waitees).

              Run the job with the given nice value. See man nice(2).  On
              Windows, values less than -15 set the process class to "High";
              -1 through -15 set "Above Normal"; 1 through 15 "Below Normal";
              and above 15 "Idle" priority class.

              Set the I/O priority value of this job. Linux limits us to a
              positive value between 0 and 7, with 0 being the highest. See
              man ionice(1). Refer to an appropriate manpage for other
              operating systems since meaning of priority may differ.

              Set the I/O priority class. See man ionice(1).

              Set the CPU affinity of this job. The parameter given is a bit
              mask of allowed CPUs the job may run on. So if you want the
              allowed CPUs to be 1 and 5, you would pass the decimal value of
              (1 << 1 | 1 << 5), or 34. See man sched_setaffinity(2). This may
              not work on all supported operating systems or kernel versions.
              This option doesn't work well for a higher CPU count than what
              you can store in an integer mask, so it can only control cpus
              1-32. For boxes with larger CPU counts, use cpus_allowed.

              Controls the same options as cpumask, but accepts a textual
              specification of the permitted CPUs instead. So to use CPUs 1
              and 5 you would specify `cpus_allowed=1,5'. This option also
              allows a range of CPUs to be specified -- say you wanted a
              binding to CPUs 1, 5, and 8 to 15, you would set

              Set the policy of how fio distributes the CPUs specified by
              cpus_allowed or cpumask. Two policies are supported:

                     shared All jobs will share the CPU set specified.

                     split  Each job will get a unique CPU from the CPU set.

              shared is the default behavior, if the option isn't specified.
              If split is specified, then fio will will assign one cpu per
              job. If not enough CPUs are given for the jobs listed, then fio
              will roundrobin the CPUs in the set.

              Set this job running on specified NUMA nodes' CPUs. The
              arguments allow comma delimited list of cpu numbers, A-B ranges,
              or `all'. Note, to enable NUMA options support, fio must be
              built on a system with libnuma-dev(el) installed.

              Set this job's memory policy and corresponding NUMA nodes.
              Format of the arguments:


              `mode' is one of the following memory poicies: `default',
              `prefer', `bind', `interleave' or `local'. For `default' and
              `local' memory policies, no node needs to be specified. For
              `prefer', only one node is allowed. For `bind' and `interleave'
              the `nodelist' may be as follows: a comma delimited list of
              numbers, A-B ranges, or `all'.

              Add job to this control group. If it doesn't exist, it will be
              created. The system must have a mounted cgroup blkio mount point
              for this to work. If your system doesn't have it mounted, you
              can do so with:

                     # mount -t cgroup -o blkio none /cgroup

              Set the weight of the cgroup to this value. See the
              documentation that comes with the kernel, allowed values are in
              the range of 100..1000.

              Normally fio will delete the cgroups it has created after the
              job completion. To override this behavior and to leave cgroups
              around after the job completion, set `cgroup_nodelete=1'. This
              can be useful if one wants to inspect various cgroup files after
              job completion. Default: false.

              The ID of the flow. If not specified, it defaults to being a
              global flow. See flow.

              Weight in token-based flow control. If this value is used, then
              there is a 'flow counter' which is used to regulate the
              proportion of activity between two or more jobs. Fio attempts to
              keep this flow counter near zero. The flow parameter stands for
              how much should be added or subtracted to the flow counter on
              each iteration of the main I/O loop. That is, if one job has
              `flow=8' and another job has `flow=-1', then there will be a
              roughly 1:8 ratio in how much one runs vs the other.

              The maximum value that the absolute value of the flow counter is
              allowed to reach before the job must wait for a lower value of
              the counter.

              The period of time, in microseconds, to wait after the flow
              watermark has been exceeded before retrying operations.

       stonewall, wait_for_previous
              Wait for preceding jobs in the job file to exit, before starting
              this one. Can be used to insert serialization points in the job
              file. A stone wall also implies starting a new reporting group,
              see group_reporting.

              By default, fio will continue running all other jobs when one
              job finishes but sometimes this is not the desired action.
              Setting exitall will instead make fio terminate all other jobs
              when one job finishes.

              Before running this job, issue the command specified through
              system(3). Output is redirected in a file called

              After the job completes, issue the command specified though
              system(3). Output is redirected in a file called

              Instead of running as the invoking user, set the user ID to this
              value before the thread/process does any work.

              Set group ID, see uid.

              Do not perform specified workload, only verify data still
              matches previous invocation of this workload. This option allows
              one to check data multiple times at a later date without
              overwriting it. This option makes sense only for workloads that
              write data, and does not support workloads with the time_based
              option set.

              Run the verify phase after a write phase. Only valid if verify
              is set. Default: true.

              If writing to a file, fio can verify the file contents after
              each iteration of the job. Each verification method also implies
              verification of special header, which is written to the
              beginning of each block. This header also includes meta
              information, like offset of the block, block number, timestamp
              when block was written, etc. verify can be combined with
              verify_pattern option. The allowed values are:

                     md5    Use an md5 sum of the data area and store it in
                            the header of each block.

                     crc64  Use an experimental crc64 sum of the data area and
                            store it in the header of each block.

                     crc32c Use a crc32c sum of the data area and store it in
                            the header of each block. This will automatically
                            use hardware acceleration (e.g. SSE4.2 on an x86
                            or CRC crypto extensions on ARM64) but will fall
                            back to software crc32c if none is found.
                            Generally the fatest checksum fio supports when
                            hardware accelerated.

                            Synonym for crc32c.

                     crc32  Use a crc32 sum of the data area and store it in
                            the header of each block.

                     crc16  Use a crc16 sum of the data area and store it in
                            the header of each block.

                     crc7   Use a crc7 sum of the data area and store it in
                            the header of each block.

                     xxhash Use xxhash as the checksum function. Generally the
                            fastest software checksum that fio supports.

                     sha512 Use sha512 as the checksum function.

                     sha256 Use sha256 as the checksum function.

                     sha1   Use optimized sha1 as the checksum function.

                            Use optimized sha3-224 as the checksum function.

                            Use optimized sha3-256 as the checksum function.

                            Use optimized sha3-384 as the checksum function.

                            Use optimized sha3-512 as the checksum function.

                     meta   This option is deprecated, since now meta
                            information is included in generic verification
                            header and meta verification happens by default.
                            For detailed information see the description of
                            the verify setting. This option is kept because of
                            compatibility's sake with old configurations. Do
                            not use it.

                            Verify a strict pattern. Normally fio includes a
                            header with some basic information and
                            checksumming, but if this option is set, only the
                            specific pattern set with verify_pattern is

                     null   Only pretend to verify. Useful for testing
                            internals with `ioengine=null', not for much else.

              This option can be used for repeated burn-in tests of a system
              to make sure that the written data is also correctly read back.
              If the data direction given is a read or random read, fio will
              assume that it should verify a previously written file. If the
              data direction includes any form of write, the verify will be of
              the newly written data.

              If true, fio will sort written verify blocks when it deems it
              faster to read them back in a sorted manner. This is often the
              case when overwriting an existing file, since the blocks are
              already laid out in the file system. You can ignore this option
              unless doing huge amounts of really fast I/O where the red-black
              tree sorting CPU time becomes significant. Default: true.

              Pre-load and sort verify blocks for a read workload.

              Swap the verification header with data somewhere else in the
              block before writing. It is swapped back before verifying.

              Write the verification header at a finer granularity than the
              blocksize. It will be written for chunks the size of
              verify_interval. blocksize should divide this evenly.

              If set, fio will fill the I/O buffers with this pattern. Fio
              defaults to filling with totally random bytes, but sometimes
              it's interesting to fill with a known pattern for I/O
              verification purposes. Depending on the width of the pattern,
              fio will fill 1/2/3/4 bytes of the buffer at the time (it can be
              either a decimal or a hex number). The verify_pattern if larger
              than a 32-bit quantity has to be a hex number that starts with
              either "0x" or "0X". Use with verify. Also, verify_pattern
              supports %o format, which means that for each block offset will
              be written and then verified back, e.g.:


              Or use combination of everything:


              Normally fio will keep checking the entire contents before
              quitting on a block verification failure. If this option is set,
              fio will exit the job on the first observed failure. Default:

              If set, dump the contents of both the original data block and
              the data block we read off disk to files. This allows later
              analysis to inspect just what kind of data corruption occurred.
              Off by default.

              Fio will normally verify I/O inline from the submitting thread.
              This option takes an integer describing how many async offload
              threads to create for I/O verification instead, causing fio to
              offload the duty of verifying I/O contents to one or more
              separate threads. If using this offload option, even sync I/O
              engines can benefit from using an iodepth setting higher than 1,
              as it allows them to have I/O in flight while verifies are
              running.  Defaults to 0 async threads, i.e. verification is not

              Tell fio to set the given CPU affinity on the async I/O
              verification threads. See cpus_allowed for the format used.

              Fio will normally verify the written contents of a job that
              utilizes verify once that job has completed. In other words,
              everything is written then everything is read back and verified.
              You may want to verify continually instead for a variety of
              reasons. Fio stores the meta data associated with an I/O block
              in memory, so for large verify workloads, quite a bit of memory
              would be used up holding this meta data. If this option is
              enabled, fio will write only N blocks before verifying these

              Control how many blocks fio will verify if verify_backlog is
              set. If not set, will default to the value of verify_backlog
              (meaning the entire queue is read back and verified). If
              verify_backlog_batch is less than verify_backlog then not all
              blocks will be verified, if verify_backlog_batch is larger than
              verify_backlog, some blocks will be verified more than once.

              When a job exits during the write phase of a verify workload,
              save its current state. This allows fio to replay up until that
              point, if the verify state is loaded for the verify read phase.
              The format of the filename is, roughly:


              <type> is "local" for a local run, "sock" for a client/server
              socket connection, and "ip" (, for instance) for a
              networked client/server connection. Defaults to true.

              If a verify termination trigger was used, fio stores the current
              write state of each thread. This can be used at verification
              time so that fio knows how far it should verify. Without this
              information, fio will run a full verification pass, according to
              the settings in the job file used. Default false.

              Number of verify blocks to discard/trim.

              Verify that trim/discarded blocks are returned as zeros.

              Verify that trim/discarded blocks are returned as zeros.

              Trim this number of I/O blocks.

              Enable experimental verification.

   Steady state
       steadystate=str:float, ss=str:float
              Define the criterion and limit for assessing steady state
              performance. The first parameter designates the criterion
              whereas the second parameter sets the threshold. When the
              criterion falls below the threshold for the specified duration,
              the job will stop. For example, `iops_slope:0.1%' will direct
              fio to terminate the job when the least squares regression slope
              falls below 0.1% of the mean IOPS. If group_reporting is enabled
              this will apply to all jobs in the group. Below is the list of
              available steady state assessment criteria. All assessments are
              carried out using only data from the rolling collection window.
              Threshold limits can be expressed as a fixed value or as a
              percentage of the mean in the collection window.

                     iops   Collect IOPS data. Stop the job if all individual
                            IOPS measurements are within the specified limit
                            of the mean IOPS (e.g., `iops:2' means that all
                            individual IOPS values must be within 2 of the
                            mean, whereas `iops:0.2%' means that all
                            individual IOPS values must be within 0.2% of the
                            mean IOPS to terminate the job).

                            Collect IOPS data and calculate the least squares
                            regression slope. Stop the job if the slope falls
                            below the specified limit.

                     bw     Collect bandwidth data. Stop the job if all
                            individual bandwidth measurements are within the
                            specified limit of the mean bandwidth.

                            Collect bandwidth data and calculate the least
                            squares regression slope. Stop the job if the
                            slope falls below the specified limit.

       steadystate_duration=time, ss_dur=time
              A rolling window of this duration will be used to judge whether
              steady state has been reached. Data will be collected once per
              second. The default is 0 which disables steady state detection.
              When the unit is omitted, the value is interpreted in seconds.

       steadystate_ramp_time=time, ss_ramp=time
              Allow the job to run for the specified duration before beginning
              data collection for checking the steady state job termination
              criterion. The default is 0. When the unit is omitted, the value
              is interpreted in seconds.

   Measurements and reporting
              If set, this generates bw/clat/iops log with per file private
              filenames. If not set, jobs with identical names will share the
              log filename. Default: true.

              It may sometimes be interesting to display statistics for groups
              of jobs as a whole instead of for each individual job. This is
              especially true if numjobs is used; looking at individual
              thread/process output quickly becomes unwieldy. To see the final
              report per-group instead of per-job, use group_reporting. Jobs
              in a file will be part of the same reporting group, unless if
              separated by a stonewall, or by using new_group.

              Start a new reporting group. See: group_reporting. If not given,
              all jobs in a file will be part of the same reporting group,
              unless separated by a stonewall.

              By default, fio collects and shows final output results for all
              jobs that run. If this option is set to 0, then fio will ignore
              it in the final stat output.

              If given, write a bandwidth log for this job. Can be used to
              store data of the bandwidth of the jobs in their lifetime.

              If no str argument is given, the default filename of
              `jobname_type.x.log' is used. Even when the argument is given,
              fio will still append the type of log. So if one specifies:


              The actual log name will be `foo_bw.x.log' where `x' is the
              index of the job (1..N, where N is the number of jobs). If
              per_job_logs is false, then the filename will not include the
              `.x` job index.

              The included fio_generate_plots script uses gnuplot to turn
              these text files into nice graphs. See the LOG FILE FORMATS
              section for how data is structured within the file.

              Same as write_bw_log, except this option creates I/O submission
              (e.g., `name_slat.x.log'), completion (e.g., `name_clat.x.log'),
              and total (e.g., `name_lat.x.log') latency files instead. See
              write_bw_log for details about the filename format and the LOG
              FILE FORMATS section for how data is structured within the

              Same as write_bw_log but writes an I/O completion latency
              histogram file (e.g., `name_hist.x.log') instead. Note that this
              file will be empty unless log_hist_msec has also been set.  See
              write_bw_log for details about the filename format and the LOG
              FILE FORMATS section for how data is structured within the file.

              Same as write_bw_log, but writes an IOPS file (e.g.
              `name_iops.x.log') instead. See write_bw_log for details about
              the filename format and the LOG FILE FORMATS section for how
              data is structured within the file.

              By default, fio will log an entry in the iops, latency, or bw
              log for every I/O that completes. When writing to the disk log,
              that can quickly grow to a very large size. Setting this option
              makes fio average the each log entry over the specified period
              of time, reducing the resolution of the log. See log_max_value
              as well. Defaults to 0, logging all entries.  Also see LOG FILE
              FORMATS section.

              Same as log_avg_msec, but logs entries for completion latency
              histograms. Computing latency percentiles from averages of
              intervals using log_avg_msec is inaccurate. Setting this option
              makes fio log histogram entries over the specified period of
              time, reducing log sizes for high IOPS devices while retaining
              percentile accuracy. See log_hist_coarseness and write_hist_log
              as well.  Defaults to 0, meaning histogram logging is disabled.

              Integer ranging from 0 to 6, defining the coarseness of the
              resolution of the histogram logs enabled with log_hist_msec. For
              each increment in coarseness, fio outputs half as many bins.
              Defaults to 0, for which histogram logs contain 1216 latency
              bins. See LOG FILE FORMATS section.

              If log_avg_msec is set, fio logs the average over that window.
              If you instead want to log the maximum value, set this option to
              1. Defaults to 0, meaning that averaged values are logged.

              If this is set, the iolog options will include the byte offset
              for the I/O entry as well as the other data values. Defaults to
              0 meaning that offsets are not present in logs. Also see LOG
              FILE FORMATS section.

              If this is set, fio will compress the I/O logs as it goes, to
              keep the memory footprint lower. When a log reaches the
              specified size, that chunk is removed and compressed in the
              background. Given that I/O logs are fairly highly compressible,
              this yields a nice memory savings for longer runs. The downside
              is that the compression will consume some background CPU cycles,
              so it may impact the run. This, however, is also true if the
              logging ends up consuming most of the system memory. So pick
              your poison. The I/O logs are saved normally at the end of a
              run, by decompressing the chunks and storing them in the
              specified log file. This feature depends on the availability of

              Define the set of CPUs that are allowed to handle online log
              compression for the I/O jobs. This can provide better isolation
              between performance sensitive jobs, and background compression

              If set, fio will store the log files in a compressed format.
              They can be decompressed with fio, using the --inflate-log
              command line parameter. The files will be stored with a `.fz'

              If set, fio will log Unix timestamps to the log files produced
              by enabling write_type_log for each log type, instead of the
              default zero-based timestamps.

              If set, record errors in trim block-sized units from writes and
              trims and output a histogram of how many trims it took to get to
              errors, and what kind of error was encountered.

              Average the calculated bandwidth over the given time. Value is
              specified in milliseconds. If the job also does bandwidth
              logging through write_bw_log, then the minimum of this option
              and log_avg_msec will be used. Default: 500ms.

              Average the calculated IOPS over the given time. Value is
              specified in milliseconds. If the job also does IOPS logging
              through write_iops_log, then the minimum of this option and
              log_avg_msec will be used. Default: 500ms.

              Generate disk utilization statistics, if the platform supports
              it.  Default: true.

              Disable measurements of total latency numbers. Useful only for
              cutting back the number of calls to gettimeofday(2), as that
              does impact performance at really high IOPS rates. Note that to
              really get rid of a large amount of these calls, this option
              must be used with disable_slat and disable_bw_measurement as

              Disable measurements of completion latency numbers. See

              Disable measurements of submission latency numbers. See

       disable_bw_measurement=bool, disable_bw=bool
              Disable measurements of throughput/bandwidth numbers. See

              Enable the reporting of percentiles of completion latencies.
              This option is mutually exclusive with lat_percentiles.

              Enable the reporting of percentiles of I/O latencies. This is
              similar to clat_percentiles, except that this includes the
              submission latency.  This option is mutually exclusive with

              Overwrite the default list of percentiles for completion
              latencies and the block error histogram. Each number is a
              floating number in the range (0,100], and the maximum length of
              the list is 20. Use ':' to separate the numbers, and list the
              numbers in ascending order. For example,
              `--percentile_list=99.5:99.9' will cause fio to report the
              values of completion latency below which 99.5% and 99.9% of the
              observed latencies fell, respectively.

              If using --output-format of `normal', set the significant
              figures to this value. Higher values will yield more precise
              IOPS and throughput units, while lower values will round.
              Requires a minimum value of 1 and a maximum value of 10.
              Defaults to 4.

   Error handling
              When one job finishes in error, terminate the rest. The default
              is to wait for each job to finish.

              Normally fio will exit the job on the first observed failure. If
              this option is set, fio will continue the job when there is a
              'non-fatal error' (EIO or EILSEQ) until the runtime is exceeded
              or the I/O size specified is completed. If this option is used,
              there are two more stats that are appended, the total error
              count and the first error. The error field given in the stats is
              the first error that was hit during the run.  The allowed values

                     none   Exit on any I/O or verify errors.

                     read   Continue on read errors, exit on all others.

                     write  Continue on write errors, exit on all others.

                     io     Continue on any I/O error, exit on all others.

                     verify Continue on verify errors, exit on all others.

                     all    Continue on all errors.

                     0      Backward-compatible alias for 'none'.

                     1      Backward-compatible alias for 'all'.

              Sometimes you want to ignore some errors during test in that
              case you can specify error list for each error type, instead of
              only being able to ignore the default 'non-fatal error' using
              errors for given error type is separated with ':'. Error may be
              symbol ('ENOSPC', 'ENOMEM') or integer. Example:


              This option will ignore EAGAIN from READ, and ENOSPC and
              122(EDQUOT) from WRITE. This option works by overriding
              continue_on_error with the list of errors for each error type if

              If set dump every error even if it is non fatal, true by
              default. If disabled only fatal error will be dumped.

   Running predefined workloads
       Fio includes predefined profiles that mimic the I/O workloads generated
       by other tools.

              The predefined workload to run. Current profiles are:

                            Threaded I/O bench (tiotest/tiobench) like

                     act    Aerospike Certification Tool (ACT) like workload.

       To view a profile's additional options use --cmdhelp after specifying
       the profile. For example:

              $ fio --profile=act --cmdhelp

   Act profile options
              Devices to use.

              ACT load multiplier. Default: 1.

              How long the entire test takes to run. When the unit is omitted,
              the value is given in seconds. Default: 24h.

              Number of read I/O threads per device. Default: 8.

              Number of 512B blocks to read at the time. Default: 3.

              Size of large block ops in KiB (writes). Default: 131072.

       prep   Set to run ACT prep phase.

   Tiobench profile options
              Size in MiB.

              Block size in bytes. Default: 4096.

              Number of runs.

              Test directory.

              Number of threads.

       Fio spits out a lot of output. While running, fio will display the
       status of the jobs created. An example of that would be:

                 Jobs: 1 (f=1): [_(1),M(1)][24.8%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 01m:31s]

       The characters inside the first set of square brackets denote the
       current status of each thread. The first character is the first job
       defined in the job file, and so forth. The possible values (in typical
       life cycle order) are:

              P      Thread setup, but not started.
              C      Thread created.
              I      Thread initialized, waiting or generating necessary data.
              p      Thread running pre-reading file(s).
              /      Thread is in ramp period.
              R      Running, doing sequential reads.
              r      Running, doing random reads.
              W      Running, doing sequential writes.
              w      Running, doing random writes.
              M      Running, doing mixed sequential reads/writes.
              m      Running, doing mixed random reads/writes.
              D      Running, doing sequential trims.
              d      Running, doing random trims.
              F      Running, currently waiting for fsync(2).
              V      Running, doing verification of written data.
              f      Thread finishing.
              E      Thread exited, not reaped by main thread yet.
              -      Thread reaped.
              X      Thread reaped, exited with an error.
              K      Thread reaped, exited due to signal.

       Fio will condense the thread string as not to take up more space on the
       command line than needed. For instance, if you have 10 readers and 10
       writers running, the output would look like this:

                 Jobs: 20 (f=20): [R(10),W(10)][4.0%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 57m:36s]

       Note that the status string is displayed in order, so it's possible to
       tell which of the jobs are currently doing what. In the example above
       this means that jobs 1--10 are readers and 11--20 are writers.

       The other values are fairly self explanatory -- number of threads
       currently running and doing I/O, the number of currently open files
       (f=), the estimated completion percentage, the rate of I/O since last
       check (read speed listed first, then write speed and optionally trim
       speed) in terms of bandwidth and IOPS, and time to completion for the
       current running group. It's impossible to estimate runtime of the
       following groups (if any).

       When fio is done (or interrupted by Ctrl-C), it will show the data for
       each thread, group of threads, and disks in that order. For each
       overall thread (or group) the output looks like:

                 Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
                   write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
                     slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
                     clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
                      lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
                     clat percentiles (usec):
                      |  1.00th=[  302],  5.00th=[  326], 10.00th=[  343], 20.00th=[  363],
                      | 30.00th=[  392], 40.00th=[  404], 50.00th=[  416], 60.00th=[  445],
                      | 70.00th=[  816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
                      | 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
                      | 99.99th=[78119]
                    bw (  KiB/s): min=  532, max=  686, per=0.10%, avg=622.87, stdev=24.82, samples=  100
                    iops        : min=   76, max=   98, avg=88.98, stdev= 3.54, samples=  100
                   lat (usec)   : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
                   lat (msec)   : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
                   lat (msec)   : 100=0.65%
                   cpu          : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
                   IO depths    : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
                      submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
                      complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
                      issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
                      latency   : target=0, window=0, percentile=100.00%, depth=8

       The job name (or first job's name when using group_reporting) is
       printed, along with the group id, count of jobs being aggregated, last
       error id seen (which is 0 when there are no errors), pid/tid of that
       thread and the time the job/group completed. Below are the I/O
       statistics for each data direction performed (showing writes in the
       example above). In the order listed, they denote:

                     The string before the colon shows the I/O direction the
                     statistics are for. IOPS is the average I/Os performed
                     per second. BW is the average bandwidth rate shown as:
                     value in power of 2 format (value in power of 10 format).
                     The last two values show: (total I/O performed in power
                     of 2 format / runtime of that thread).

              slat   Submission latency (min being the minimum, max being the
                     maximum, avg being the average, stdev being the standard
                     deviation). This is the time it took to submit the I/O.
                     For sync I/O this row is not displayed as the slat is
                     really the completion latency (since queue/complete is
                     one operation there).  This value can be in nanoseconds,
                     microseconds or milliseconds --- fio will choose the most
                     appropriate base and print that (in the example above
                     nanoseconds was the best scale). Note: in --minimal mode
                     latencies are always expressed in microseconds.

              clat   Completion latency. Same names as slat, this denotes the
                     time from submission to completion of the I/O pieces. For
                     sync I/O, clat will usually be equal (or very close) to
                     0, as the time from submit to complete is basically just
                     CPU time (I/O has already been done, see slat

              lat    Total latency. Same names as slat and clat, this denotes
                     the time from when fio created the I/O unit to completion
                     of the I/O operation.

              bw     Bandwidth statistics based on samples. Same names as the
                     xlat stats, but also includes the number of samples taken
                     (samples) and an approximate percentage of total
                     aggregate bandwidth this thread received in its group
                     (per). This last value is only really useful if the
                     threads in this group are on the same disk, since they
                     are then competing for disk access.

              iops   IOPS statistics based on samples. Same names as bw.

              lat (nsec/usec/msec)
                     The distribution of I/O completion latencies. This is the
                     time from when I/O leaves fio and when it gets completed.
                     Unlike the separate read/write/trim sections above, the
                     data here and in the remaining sections apply to all I/Os
                     for the reporting group. 250=0.04% means that 0.04% of
                     the I/Os completed in under 250us. 500=64.11% means that
                     64.11% of the I/Os required 250 to 499us for completion.

              cpu    CPU usage. User and system time, along with the number of
                     context switches this thread went through, usage of
                     system and user time, and finally the number of major and
                     minor page faults. The CPU utilization numbers are
                     averages for the jobs in that reporting group, while the
                     context and fault counters are summed.

              IO depths
                     The distribution of I/O depths over the job lifetime. The
                     numbers are divided into powers of 2 and each entry
                     covers depths from that value up to those that are lower
                     than the next entry -- e.g., 16= covers depths from 16 to
                     31. Note that the range covered by a depth distribution
                     entry can be different to the range covered by the
                     equivalent submit/complete distribution entry.

              IO submit
                     How many pieces of I/O were submitting in a single submit
                     call. Each entry denotes that amount and below, until the
                     previous entry -- e.g., 16=100% means that we submitted
                     anywhere between 9 to 16 I/Os per submit call. Note that
                     the range covered by a submit distribution entry can be
                     different to the range covered by the equivalent depth
                     distribution entry.

              IO complete
                     Like the above submit number, but for completions

              IO issued rwt
                     The number of read/write/trim requests issued, and how
                     many of them were short or dropped.

              IO latency
                     These values are for latency_target and related options.
                     When these options are engaged, this section describes
                     the I/O depth required to meet the specified latency

       After each client has been listed, the group statistics are printed.
       They will look like this:

                 Run status group 0 (all jobs):
                    READ: bw=20.9MiB/s (21.9MB/s), 10.4MiB/s-10.8MiB/s (10.9MB/s-11.3MB/s), io=64.0MiB (67.1MB), run=2973-3069msec
                   WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec

       For each data direction it prints:

              bw     Aggregate bandwidth of threads in this group followed by
                     the minimum and maximum bandwidth of all the threads in
                     this group.  Values outside of brackets are power-of-2
                     format and those within are the equivalent value in a
                     power-of-10 format.

              io     Aggregate I/O performed of all threads in this group. The
                     format is the same as bw.

              run    The smallest and longest runtimes of the threads in this

       And finally, the disk statistics are printed. This is Linux specific.
       They will look like this:

                   Disk stats (read/write):
                     sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%

       Each value is printed for both reads and writes, with reads first. The
       numbers denote:

              ios    Number of I/Os performed by all groups.

              merge  Number of merges performed by the I/O scheduler.

              ticks  Number of ticks we kept the disk busy.

                     Total time spent in the disk queue.

              util   The disk utilization. A value of 100% means we kept the
                     disk busy constantly, 50% would be a disk idling half of
                     the time.

       It is also possible to get fio to dump the current output while it is
       running, without terminating the job. To do that, send fio the USR1
       signal. You can also get regularly timed dumps by using the
       --status-interval parameter, or by creating a file in `/tmp' named
       `fio-dump-status'. If fio sees this file, it will unlink it and dump
       the current output status.

       For scripted usage where you typically want to generate tables or
       graphs of the results, fio can output the results in a semicolon
       separated format. The format is one long line of values, such as:

                 A description of this job goes here.

       The job description (if provided) follows on a second line.

       To enable terse output, use the --minimal or `--output-format=terse'
       command line options. The first value is the version of the terse
       output format. If the output has to be changed for some reason, this
       number will be incremented by 1 to signify that change.

       Split up, the format is as follows (comments in brackets denote when a
       field was introduced or whether it's specific to some terse version):

                      terse version, fio version [v3], jobname, groupid, error

              READ status:

                      Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
                      Submission latency: min, max, mean, stdev (usec)
                      Completion latency: min, max, mean, stdev (usec)
                      Completion latency percentiles: 20 fields (see below)
                      Total latency: min, max, mean, stdev (usec)
                      Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
                      IOPS [v5]: min, max, mean, stdev, number of samples

              WRITE status:

                      Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
                      Submission latency: min, max, mean, stdev (usec)
                      Completion latency: min, max, mean, stdev (usec)
                      Completion latency percentiles: 20 fields (see below)
                      Total latency: min, max, mean, stdev (usec)
                      Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
                      IOPS [v5]: min, max, mean, stdev, number of samples

              TRIM status [all but version 3]:

                      Fields are similar to READ/WRITE status.

              CPU usage:

                      user, system, context switches, major faults, minor faults

              I/O depths:

                      <=1, 2, 4, 8, 16, 32, >=64

              I/O latencies microseconds:

                      <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000

              I/O latencies milliseconds:

                      <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000

              Disk utilization [v3]:

                      disk name, read ios, write ios, read merges, write merges, read ticks, write ticks, time spent in queue, disk utilization percentage

              Additional Info (dependent on continue_on_error, default off):

                      total # errors, first error code

              Additional Info (dependent on description being set):

                      Text description

       Completion latency percentiles can be a grouping of up to 20 sets, so
       for the terse output fio writes all of them. Each field will look like


       which is the Xth percentile, and the `usec' latency associated with it.

       For Disk utilization, all disks used by fio are shown. So for each disk
       there will be a disk utilization section.

       Below is a single line containing short names for each of the fields in
       the minimal output v3, separated by semicolons:


       The json output format is intended to be both human readable and
       convenient for automated parsing. For the most part its sections mirror
       those of the normal output. The runtime value is reported in msec and
       the bw value is reported in 1024 bytes per second units.

       The json+ output format is identical to the json output format except
       that it adds a full dump of the completion latency bins. Each bins
       object contains a set of (key, value) pairs where keys are latency
       durations and values count how many I/Os had completion latencies of
       the corresponding duration. For example, consider:

              "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1,
              "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" :
              534, "105984" : 5995, "107008" : 7529, ... }

       This data indicates that one I/O required 87,552ns to complete, two
       I/Os required 100,864ns to complete, and 7529 I/Os required 107,008ns
       to complete.

       Also included with fio is a Python script fio_jsonplus_clat2csv that
       takes json+ output and generates CSV-formatted latency data suitable
       for plotting.

       The latency durations actually represent the midpoints of latency
       intervals.  For details refer to `stat.h' in the fio source.

       There are two trace file format that you can encounter. The older (v1)
       format is unsupported since version 1.20-rc3 (March 2008). It will
       still be described below in case that you get an old trace and want to
       understand it.

       In any case the trace is a simple text file with a single action per

       Trace file format v1
              Each line represents a single I/O action in the following

                     rw, offset, length

              where `rw=0/1' for read/write, and the `offset' and `length'
              entries being in bytes.

              This format is not supported in fio versions >= 1.20-rc3.

       Trace file format v2
              The second version of the trace file format was added in fio
              version 1.17. It allows to access more then one file per trace
              and has a bigger set of possible file actions.

              The first line of the trace file has to be:

                     "fio version 2 iolog"

              Following this can be lines in two different formats, which are
              described below.

              The file management format:
                     filename action

                     The `filename' is given as an absolute path. The `action'
                     can be one of these:

                            add    Add the given `filename' to the trace.

                            open   Open the file with the given `filename'.
                                   The `filename' has to have been added with
                                   the add action before.

                            close  Close the file with the given `filename'.
                                   The file has to have been opened before.

              The file I/O action format:
                     filename action offset length

                     The `filename' is given as an absolute path, and has to
                     have been added and opened before it can be used with
                     this format. The `offset' and `length' are given in
                     bytes. The `action' can be one of these:

                            wait   Wait for `offset' microseconds. Everything
                                   below 100 is discarded.  The time is
                                   relative to the previous `wait' statement.

                            read   Read `length' bytes beginning from

                            write  Write `length' bytes beginning from

                            sync   fsync(2) the file.

                                   fdatasync(2) the file.

                            trim   Trim the given file from the given `offset'
                                   for `length' bytes.

       In some cases, we want to understand CPU overhead in a test. For
       example, we test patches for the specific goodness of whether they
       reduce CPU usage.  Fio implements a balloon approach to create a thread
       per CPU that runs at idle priority, meaning that it only runs when
       nobody else needs the cpu.  By measuring the amount of work completed
       by the thread, idleness of each CPU can be derived accordingly.

       An unit work is defined as touching a full page of unsigned characters.
       Mean and standard deviation of time to complete an unit work is
       reported in "unit work" section. Options can be chosen to report
       detailed percpu idleness or overall system idleness by aggregating
       percpu stats.

       Fio is usually run in one of two ways, when data verification is done.
       The first is a normal write job of some sort with verify enabled. When
       the write phase has completed, fio switches to reads and verifies
       everything it wrote. The second model is running just the write phase,
       and then later on running the same job (but with reads instead of
       writes) to repeat the same I/O patterns and verify the contents. Both
       of these methods depend on the write phase being completed, as fio
       otherwise has no idea how much data was written.

       With verification triggers, fio supports dumping the current write
       state to local files. Then a subsequent read verify workload can load
       this state and know exactly where to stop. This is useful for testing
       cases where power is cut to a server in a managed fashion, for

       A verification trigger consists of two things:

              1) Storing the write state of each job.

              2) Executing a trigger command.

       The write state is relatively small, on the order of hundreds of bytes
       to single kilobytes. It contains information on the number of
       completions done, the last X completions, etc.

       A trigger is invoked either through creation ('touch') of a specified
       file in the system, or through a timeout setting. If fio is run with
       `--trigger-file=/tmp/trigger-file', then it will continually check for
       the existence of `/tmp/trigger-file'. When it sees this file, it will
       fire off the trigger (thus saving state, and executing the trigger

       For client/server runs, there's both a local and remote trigger. If fio
       is running as a server backend, it will send the job states back to the
       client for safe storage, then execute the remote trigger, if specified.
       If a local trigger is specified, the server will still send back the
       write state, but the client will then execute the trigger.

       Verification trigger example
              Let's say we want to run a powercut test on the remote Linux
              machine 'server'.  Our write workload is in `write-test.fio'. We
              want to cut power to 'server' at some point during the run, and
              we'll run this test from the safety or our local machine,
              'localbox'. On the server, we'll start the fio backend normally:

                     server# fio --server

              and on the client, we'll fire off the workload:

                     localbox$ fio --client=server
                     --trigger-file=/tmp/my-trigger --trigger-remote="bash -c
                     "echo b > /proc/sysrq-triger""

              We set `/tmp/my-trigger' as the trigger file, and we tell fio to

                     echo b > /proc/sysrq-trigger

              on the server once it has received the trigger and sent us the
              write state. This will work, but it's not really cutting power
              to the server, it's merely abruptly rebooting it. If we have a
              remote way of cutting power to the server through IPMI or
              similar, we could do that through a local trigger command
              instead. Let's assume we have a script that does IPMI reboot of
              a given hostname, ipmi-reboot. On localbox, we could then have
              run fio with a local trigger instead:

                     localbox$ fio --client=server
                     --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot

              For this case, fio would wait for the server to send us the
              write state, then execute `ipmi-reboot server' when that

       Loading verify state
              To load stored write state, a read verification job file must
              contain the verify_state_load option. If that is set, fio will
              load the previously stored state. For a local fio run this is
              done by loading the files directly, and on a client/server run,
              the server backend will ask the client to send the files over
              and load them from there.

       Fio supports a variety of log file formats, for logging latencies,
       bandwidth, and IOPS. The logs share a common format, which looks like

              time (msec), value, data direction, block size (bytes), offset

       `Time' for the log entry is always in milliseconds. The `value' logged
       depends on the type of log, it will be one of the following:

              Latency log
                     Value is latency in nsecs

              Bandwidth log
                     Value is in KiB/sec

              IOPS log
                     Value is IOPS

       `Data direction' is one of the following:

              0      I/O is a READ

              1      I/O is a WRITE

              2      I/O is a TRIM

       The entry's `block size' is always in bytes. The `offset' is the
       offset, in bytes, from the start of the file, for that particular I/O.
       The logging of the offset can be toggled with log_offset.

       Fio defaults to logging every individual I/O. When IOPS are logged for
       individual I/Os the `value' entry will always be 1. If windowed logging
       is enabled through log_avg_msec, fio logs the average values over the
       specified period of time.  If windowed logging is enabled and
       log_max_value is set, then fio logs maximum values in that window
       instead of averages. Since `data direction', `block size' and `offset'
       are per-I/O values, if windowed logging is enabled they aren't
       applicable and will be 0.

       Normally fio is invoked as a stand-alone application on the machine
       where the I/O workload should be generated. However, the backend and
       frontend of fio can be run separately i.e., the fio server can generate
       an I/O workload on the "Device Under Test" while being controlled by a
       client on another machine.

       Start the server on the machine which has access to the storage DUT:

              $ fio --server=args

       where `args' defines what fio listens to. The arguments are of the form
       `type,hostname' or `IP,port'. `type' is either `ip' (or ip4) for TCP/IP
       v4, `ip6' for TCP/IP v6, or `sock' for a local unix domain socket.
       `hostname' is either a hostname or IP address, and `port' is the port
       to listen to (only valid for TCP/IP, not a local socket). Some

              1) fio --server
                     Start a fio server, listening on all interfaces on the
                     default port (8765).

              2) fio --server=ip:hostname,4444
                     Start a fio server, listening on IP belonging to hostname
                     and on port 4444.

              3) fio --server=ip6:::1,4444
                     Start a fio server, listening on IPv6 localhost ::1 and
                     on port 4444.

              4) fio --server=,4444
                     Start a fio server, listening on all interfaces on port

              5) fio --server=
                     Start a fio server, listening on IP on the
                     default port.

              6) fio --server=sock:/tmp/fio.sock
                     Start a fio server, listening on the local socket

       Once a server is running, a "client" can connect to the fio server

              $ fio <local-args> --client=<server> <remote-args> <job file(s)>

       where `local-args' are arguments for the client where it is running,
       `server' is the connect string, and `remote-args' and `job file(s)' are
       sent to the server. The `server' string follows the same format as it
       does on the server side, to allow IP/hostname/socket and port strings.

       Fio can connect to multiple servers this way:

              $ fio --client=<server1> <job file(s)> --client=<server2> <job

       If the job file is located on the fio server, then you can tell the
       server to load a local file as well. This is done by using

              $ fio --client=server --remote-config /path/to/file.fio

       Then fio will open this local (to the server) job file instead of being
       passed one from the client.

       If you have many servers (example: 100 VMs/containers), you can input a
       pathname of a file containing host IPs/names as the parameter value for
       the --client option. For example, here is an example `host.list' file
       containing 2 hostnames:


       The fio command would then be:

              $ fio --client=host.list <job file(s)>

       In this mode, you cannot input server-specific parameters or job files
       -- all servers receive the same job file.

       In order to let `fio --client' runs use a shared filesystem from
       multiple hosts, `fio --client' now prepends the IP address of the
       server to the filename. For example, if fio is using the directory
       `/mnt/nfs/fio' and is writing filename `fileio.tmp', with a --client
       `hostfile' containing two hostnames `h1' and `h2' with IP addresses and, then fio will create two files:


       fio was written by Jens Axboe <>.
       This man page was written by Aaron Carroll <>
       based on documentation by Jens Axboe.
       This man page was rewritten by Tomohiro Kusumi <>
       based on documentation by Jens Axboe.

       Report bugs to the fio mailing list <>.


       For further documentation see HOWTO and README.
       Sample jobfiles are available in the `examples/' directory.
       These are typically located under `/usr/share/doc/fio'.


User Manual                       August 2017                           fio(1)