Scratch storage

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(Úložiště scratch)

Scratch storage is a storage for temporary files on computing nodes. This storage should be used only during computations and should be freed after your job ends immediately.

Scratch types

We offer three types of the scratch storage

  • ultra fast but small SSD disc, mounted to directory /scratch.ssd
  • fast regular local disk, mounted to directory /scratch
  • network volume available for all the nodes of a specific cluster, mounted to directory /scratch.shared

You must set the size and type of scratch dir during job submission! There is no default type of scratch, therefore user has to specify what type of scratch should be used.

Examples:

   -l select=1:ncpus=1:mem=4gb:scratch_local=10gb
   -l select=1:ncpus=1:mem=4gb:scratch_ssd=1gb
   -l select=1:ncpus=1:mem=4gb:scratch_shared=1gb

Warning.gif Warning: Please note, that by explicit request for the ultra fast (ssd) or shared (shared) scratch space one may significantly decrease the number of nodes, which could be assigned to such a job (since most of the MetaCentrum clusters are not equipped with these scratch types -- see the list of MetaCentrum HW located at MetaCentrum webpage).

System variables

Allocated space on scratch disk is mentioned in system variable $SCRATCHDIR, which value is like /directory/username/job_jobid, ie. /scratch.ssd/username/job_2477934.arien.ics.muni.cz. Scratch type is mentioned in system variable $SCRATCH_TYPE and scratch ca[acoty in $SCRATCH_VOLUME.


Directory /scratch*/$USER is not writable (rights 555). Jobs can only write into allocated subdirectory /scratch*/$USER/job_JOBID. Please always check that your scripts are working with variable $SCRATCHDIR. If (before ending) job cleans $SCRATCHDIR itself, directory of type job_JOBID.arien.ics.muni.cz will be deleted. Otherwise, this directory will be automatically deleted after 14 days.

Note: To see the system variable type

echo $SCRATCHDIR