Backups

From StackWiki

All data in user homedirs and webdirectories is backed up (at least) daily and backups can be restored by the Unix Committee upon request at any time.

Snapshots

Homedirectories, webdirectories and most other data is stored on a NetApp fileserver ("sabretooth"). This fileserver periodically makes snapshots of the data, and a number of these snapshots are then stored alongside the live data. In any directory, these snapshots can be accessed through the hidden directory .snapshot. This makes it possible to restore your own data without needing help from the system administrators; you can just copy the file from one of the snapshots back to the normal location. The following snapshots are generally available: hourly.x, sv_daily.x. The lower the number x, the more recent the snapshot. Note that "hourly" snapshots are made six times a day, not really every hour. If you need data older than available here (approximately one week), but less than 30 days old, you can ask the Unix Committee to restore these files for you.

Caution: because of technical reasons, our systems cannot always distinguish one version from another, because the operating system caches the information. To better illustrate this: even if .snapshot/sv_daily.0/file.txt and .snapshot/sv_daily.1/file.txt differ, the operating system will just make them appear to be the same, because it has already cached the other one (technically, this is because the fsid-nodeid pair of both files is the same). As a consequence, if you have been working on a file on one system, made a mistake, and want to restore a snapshotted version, you are best off restoring the file on another system (e.g., if you were working on toad, use another login server, such as snail to restore it) so the system will not have cached the file yet. Alternatively, you can always ask the Unix Committee to restore the file(s) for you.

Beside homedirectories and webdirectories, other filer-mounted directories offer snapshots too, e.g. /ftp, /slurp, /scratch, etc. As a rule of thumb: you can use snapshots for all data that is available on more than one login server.

Some member-run systems also use the filer for homedirectories (e.g. dragon, mud). Snapshots are also available here.

Database backups

Databases (MySQL, PostgreSQL) are backed up daily. Currently, databases are stored for 90 days, but this may be reduced to 30 days in the near future. Restores are performed by the Unix Committee. Per-database restores are standard; for MySQL databases it may be possible to do per-table restores but this may result in constraint inconsistencies.

Other backups

Subversion repositories are backed up daily, as well as snapshotted using the hourly.xx scheme.

Local filesystems (e.g., /tmp, /usr, etc.) are never snapshotted. Backups may or may not be available. Generally, user data is not stored here so most likely you will not need this. Note that /tmp however is never backed up.