The /scratch file system is designed for performance rather than reliability, as a fast workspace for temporary storage. All CSCS systems provide a scratch personal folder for users that can be accessed through the environment variable $SCRATCH pointing to /scratch/<system_name>/$USER.
Piz Daint shares a Lustre scratch file system mounted on /scratch/snx3000, while clusters share a separate GPFS scratch file system under /scratch/shared. Monch has instead a dedicated internal Lustre scratch file system mounted on /mnt/lnec.
No strict quotas are enforced on /scratch, but a soft quota on the number of inodes (i.e. files and folders) is enforced on Piz Daint (/scratch/snx3000). In order to prevent a degradation of the performance, users with over 1 million files and folders will be warned at submit time and will not be able to submit new jobs.
Please note that a cleaning policy is in place on /scratch: all files older than 30 days will be deleted by a script that runs daily, so please ensure that you do not target this as a long term storage. Please note that in order to avoid performance and stability issues on the /scratch filesystem, if the occupancy grows above the critical limit of 60 % we will be forced to ask you immediate action to remove unnecessary data.
Keep also in mind that data on /scratch are NOT backed up, therefore users are advised to move valuable data to the /project filesystem as soon as batch jobs are completed. Please, do not use the "touch" command to prevent the cleaning policy from removing files, because this behaviour would deprive the community of a shared resource.
For further information, please contact us help(at)cscs.ch.