From NJIT-ARCS HPC Wiki
"Scratch space" is temporary disk under directories named /tmp, /scratch, /nscratch, or /bscratch. If local to the compute node (/tmp or /scratch), this disk is much faster than a network-mounted file system such as AFS or NFS. If mounted via NFS (/nscratch or /bscratch), it is faster than AFS space.
Scratch space is not backed up, so files erased or lost from scratch cannot be restored.
Kong /tmp, /scratch, /bscratch
- Files are automatically erased on these local filesystems after all jobs belonging to the user have ended. A nightly process deletes any files missed if the job crashed and the SGE scheduler did not run the scratch purge.
- As of April 2014, old files are only purged if there is a space shortage. During summer 2014 files older than 28 days old will be purged. The file owner will be informed of the purge when the files are 21 days old.
Stheno /tmp, /scratch
- Files are automatically erased on these local filesystems after all jobs belonging to the user have ended.