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# Backups¶

Danger

All NERSC users should back up important files to HPSS on a regular basis. Ultimately, it is your responsibility to protect yourself from data loss.

### Snapshots¶

Global homes and project use a snapshot capability to provide users a seven-day history of their directories. Every directory and sub-directory in global homes contains a ".snapshots" entry.

• .snapshots is invisble to ls, ls -a, find and similar commands
• Contents are visible through ls -F .snapshots
• Can be browsed normally after cd .snapshots
• Files cannot be created, deleted or edited in snapshots
• Files can only be copied out of a snapshot

### Backup/Restore¶

Global homes are backed up to HPSS on a regular basis. If you require a restoration of lost data that cannot be accomplished via the snapshots capability, please contact NERSC Consulting with pathnames and timestamps of the missing data. Such restore requests may take a few days to complete.

## Purging¶

Files in $SCRATCH directories may be purged if they are older than 12 weeks (defined by last access time). Warning $SCRATCH directories are not backed up