How to use ARC scratch space: Difference between revisions
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For example, if the job ID is '''1234567''', then the directory name will be <code>/scratch/1234567</code>. | For example, if the job ID is '''1234567''', then the directory name will be <code>/scratch/1234567</code>. | ||
The quota, the storage limit, for the <code>/scratch</code> file system is set to '''15TB''' and '''1 million''' files, '''per user'''. | The quota, the storage limit, for the <code>/scratch</code> file system is set to '''15TB''' and '''1 million''' files, '''per user''', at the moment of writing. The '''current storage usage''' on ARC can be checked at any moment with the <code>arc.quota</code> command. | ||
Revision as of 17:26, 19 April 2023
Background
References:
The scratch space provided on ARC is designed to handle large temporary files generated by the job during job's run time.
The scratch space is crated by SLURM when the job starts on the /scratch file systems
as a directory with the name /scratch/<job ID>.
For example, if the job ID is 1234567, then the directory name will be /scratch/1234567.
The quota, the storage limit, for the /scratch file system is set to 15TB and 1 million files, per user, at the moment of writing. The current storage usage on ARC can be checked at any moment with the arc.quota command.
If the scratch directory is empty at the end of the job, then it is deleted automatically upon job's completion.
If, however, the scratch directory in not empty and contains some data, when the job finishes, the directory is not deleted immediately, but instead it is allowed to stay for another 5 days, starting from the time of the job's end, to let the user to move the data to a proper storage location. After 5 days the scratch directory will be automatically deleted even if it still contains data.
Before the job starts, its job ID is not yet known, and the scratch directory does not yet exist.
Thus, is it impossible to stage any data into that directory before the job starts.
Any data staging, if required has to be during job's run time in the job script.
While a job is running there is a SLURM environmental variable $SLURM_JOBID is set to the actual job ID of the job.
Hence, the scratch directory can be referenced as /scratch/$SLURM_JOBID.