Introduction
The scratch space on NICS resources utilizes Lustre, a massively parallel distributed file system. This space is intended for production work and not long term storage. Files in scratch directories are not backed up and are subject to being purged after 30 days. It is the user's responsibility to back up all important data to HPSS or other storage resources.
IMPORTANT: On Kraken, Lustre is the Only File System Available to the Compute Nodes.
On Kraken, input and output files must use this area, as well as the current directory at the time aprun is called. Executables, as well as file redirects to and from aprun may be in a home directory because aprun itself runs on a service node. If you receive an error such as "No such file or directory", look for where your program is trying to access something in your home directory.Lustre scratch space can be found in the following locations on various NICS resources:
|
System |
Path |
Variable |
| Kraken | /lustre/scratch/$USER | $SCRATCHDIR |
| Nautilus | /lustre/medusa/$USER | $SCRATCHDIR |
| Keeneland | /lustre/medusa/$USER | n/a |
Purge Policy
The scratch file system should not be used for long term storage, and files on scratch are not backed up or guaranteed by NICS. In the event of a file system crash or purge, files in scratch directories cannot be recovered. It is the user's responsibility to back up all important data to HPSS or other storage resources.
Files are exempt from purge if they have been written to or read within the last 30 days. To find out if files will be purged you can use:
lfs find $SCRATCHDIR -atime +30 | xargs ls -l --time=atime --sort=time
NICS Scratch Space Purge Policy:
Modifying file access times (using "touch" or any other method) for the purpose of circumventing purge policies may result in the loss of access to the scratch file systems. Under special circumstances, users may request a purge exemption by submitting a request in a timely manner that includes detailed justification to help@xsede.org. Please include file system (e.g. Kraken: /lustre/scratch or Nautilus: /lustre/medusa ), PI of the project, user requesting exemption, TG-Account, time requested (two weeks etc.), and detailed justification.I/O and Lustre Tips
Lustre is a shared resource by all users on the system. Optimizing your IO performance will not only lessen the load on Lustre, it will save you compute time as well. Please consider reading the I/O and Lustre Tips page which we believe will help you make the best use of the parallel Lustre filesystem and improve your application's I/O performance.
Lustre Frequently Asked Questions (FAQs)
Frequently Asked Questions about Lustre are available on Lustre FAQs page.
