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Local and Scratch Storage on NREL HPC Systems#

The table below summarizes the local and scratch storage currently on NREL HPC systems.

System Name Node Local Storage $TMPDIR Default Default $TMPDIR Storage Type Global Scratch Storage
Kestrel 1.7TB on 256 of the standard compute nodes, 5.8TB on bigmem nodes. Other nodes have none. /tmp/scratch/$SLURM_JOBID Local disk when available, or RAM /scratch/$USER (Lustre)
Swift 1.8TB /scratch/$USER/$SLURM_JOBID Local disk None
Vermilion 60GB (t), 250GB (sm), 500GB (std), 1.0TB (lg), 2.0TB (gpu) /tmp RAM. Write to /tmp/scratch instead to use local disk. /scratch/$USER

Important Notes

  • Local storage is local to a node and usually faster to access by the processes running on the node. Some scenarios in which using the local disk might make your job run faster are:
    • Your job may access or create many small (temporary) files
    • Your job may have many parallel tasks accessing the same file
    • Your job may do many random reads/writes or memory mapping.
  • Local or scratch spaces are for temporary files only and there is no expectation of data longevity in these spaces. HPC users should copy results from those spaces to a /projects or global scratch directory as part of the job script before the job finishes.
  • A node will not have read or write access to any other node's local scratch, only its own
  • On Kestrel, the path /tmp/scratch is not writeable. Use $TMPDIR instead.
  • On Kestrel, only 256 of the standard compute nodes have real local disk, the other standard compute nodes have no local disk space. For the nodes without local storage, writing to $TMPDIR uses RAM. This could cause an out-of-memory error if using a lot of space in $TMPDIR. To solve this problem:
    • Use /scratch/$USER instead of the default $TMPDIR path if the job benefits little from local storage (e.g. jobs with low I/O communication)
    • Request nodes with local storage by using the --tmp option in your job submission script. (e.g. --tmp=1600000). Then, $TMPDIR will be using a local disk.
    • In addition, on Kestrel, this bash command can be used to check if there is a local disk on the node: "if [ -e /dev/nvme0n1 ]". This will only work on standard compute nodes. For example:

if [ -e /dev/nvme0n1 ]; then
 echo "This node has a local storage and will use as the scratch path"
 echo "This node does not have a local storage drive and will use /scratch as the scratch path"
This does not work on bigmem nodes. All bigmem nodes have a real local disk.