sge_ckpt

Grid(Engine)                           1                          Grid(Engine)



NAME
       Grid Engine Enterprise Edition Checkpointing - the Grid Engine
       Enterprise Edition checkpointing mechanism and checkpointing support

DESCRIPTION
       Grid Engine Enterprise Edition supports two levels of checkpointing:
       the user level and a operating system provided transparent level. User
       level checkpointing refers to applications, which do their own
       checkpointing by writing restart files at certain times or algorithmic
       steps and by properly processing these restart files when restarted.

       Transparent checkpointing has to be provided by the operating system
       and is usually integrated in the operating system kernel. An example
       for a kernel integrated checkpointing facility is the Hibernator
       package from Softway for SGI IRIX platforms.

       Checkpointing jobs need to be identified to the Grid Engine Enterprise
       Edition system by using the -ckpt option of the qsub(1) command. The
       argument to this flag refers to a so called checkpointing environment,
       which defines the attributes of the checkpointing method to be used
       (see checkpoint(5) for details).  Checkpointing environments are setup
       by the qconf(1) options -ackpt, -dckpt, -mckpt and -sckpt. The qsub(1)
       option -c can be used to overwrite the when attribute for the
       referenced checkpointing environment.

       If a queue is of the type CHECKPOINTING, jobs need to have the
       checkpointing attribute flagged (see the -ckpt option to qsub(1)) to be
       permitted to run in such a queue. As opposed to the behavior for
       regular batch jobs, checkpointing jobs are aborted under conditions,
       for which batch or interactive jobs are suspended or even stay
       unaffected. These conditions are:

       ·  Explicit suspension of the queue or job via qmod(1) by the cluster
          administration or a queue owner if the x occasion specifier (see
          qsub(1) -c and checkpoint(5)) was assigned to the job.

       ·  A load average value exceeding the migration threshold as configured
          for the corresponding queues (see queue_conf(5)).

       ·  Shutdown of the Grid Engine Enterprise Edition execution daemon
          sge_execd(8) being responsible for the checkpointing job.

       After abortion, the jobs will migrate to other queues unless they were
       submitted to one specific queue by an explicit user request.  The
       migration of jobs leads to a dynamic load balancing.  Note: The
       abortion of checkpointed jobs will free all resources (memory, swap
       space) which the job occupies at that time. This is opposed to the
       situation for suspended regular jobs, which still cover swap space.

RESTRICTIONS
       When a job migrates to a queue on another machine at present no files
       are transferred automatically to that machine. This means that all
       files which are used throughout the entire job including restart files,
       executables and scratch files must be visible or transferred explicitly
       (e.g. at the beginning of the job script).

       There are also some practical limitations regarding use of disk space
       for transparently checkpointing jobs. Checkpoints of a transparently
       checkpointed application are usually stored in a checkpoint file or
       directory by the operating system. The file or directory contains all
       the text, data, and stack space for the process, along with some
       additional control information. This means jobs which use a very large
       virtual address space will generate very large checkpoint files. Also
       the workstations on which the jobs will actually execute may have
       little free disk space. Thus it is not always possible to transfer a
       transparent checkpointing job to a machine, even though that machine is
       idle. Since large virtual memory jobs must wait for a machine that is
       both idle, and has a sufficient amount of free disk space, such jobs
       may suffer long turnaround times.

SEE ALSO
       sge_intro(1), qconf(1), qmod(1), qsub(1), checkpoint(5), Grid Engine
       Enterprise Edition Installation and Administration Guide, Grid Engine
       Enterprise Edition User's Guide

COPYRIGHT
       See sge_intro(1) for a full statement of rights and permissions.



Edition_CKPT                      Enterprise                      Grid(Engine)