Backups¶
Danger
All NERSC users should back up important files to HPSS on a regular basis. You should also have at least one copy of critical data stored outside of NERSC. Ultimately, it is your responsibility to protect yourself from data loss.
Snapshots¶
Global Homes, Global Common and Community use a snapshot capability to provide users a seven-day history of their directories. A snapshot refers to a technology that creates a point-in-time copy of data, essentially capturing the current state of a system at a specific moment, allowing users to quickly revert back to that state if needed. Running cd .snapshots
in either your $HOME
directory, your project directory under /global/common/software
or your project directory under global/cfs/cdirs
will take you to the snapshots of that directory. From there ls
will show a directory for each snapshot, named for the date of the snapshot. You can navigate to the snapshot and directory of interest, and copy files from the snapshot to a new location.
In summary:
.snapshots
is invisible tols
,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
Warning
These snapshots make it possible to recover accidentally-deleted data, but are not architected to provide disaster protection - we do not have multiple or off-site copies of data. For this reason you should ensure you have other copies, in other locations, of all critical data.
Purging¶
Note
See Filesystem Quotas and Purging for detailed information about inode, space quotas, and file system purge policies.
Warning
$SCRATCH
directories are not backed up