Backups

Data stored on hard drives has become very precious to many. In some cases, the ones and zeros written to disk can mean weeks, months or years worth of work to their author, and in other cases (such as data from a telescope run) they can never be recovered. For this reason, we not only have some redundant systems in place, but also some backup systems to try to make sure important data is never lost.

On-site backups

Snapshots

The central file server (which stores your home directory in /u) has a feature available called snapshotting. Every two hours a "snapshot" of the current state of your files is taken and frozen. This is useful if you accidentally delete a file or discover that a file is corrupt, as it means you can "roll back the clock" so to speak and recover an earlier version of your file.

Snapshots for your directory are located in the ~/.snapshot directory (you won't see it in a directory list, but it *is* there if you 'cd' to it). Under that directory you'll see other directories with names like "hourly.0" or "nightly.0". The higher the number, the older the snapshot is. hourly.0 was taken at the last even hour, hourly.1 was from two hours before that, and so on. The nightly snapshots are taken at midnight, so nightly.0 is the state of your files at midnight this morning, and nightly.1 is midnight the day before.

How to recover via snapshots

To recover a snapshot, just copy the file from the snapshot directory to anywhere in your home directory. Note that you won't be able to delete, rename, or otherwise modify anything under .snapshot as it's read only.

If you need to recover a file from your home directory older than the available snapshots, please send an e-mail to help@astro as soon as possible so we can recover it from the nightly backups which are performed on the central file server.

Off-site backups

Every night, starting around 0130, the home directory server is backed up to OIT's TSM servers. This doesn't always succeed - sometimes their servers are overloaded and backups don't complete, but that's why we have the snapshot feature turned on. Files that are backed up via TSM are kept for 90 days from the date of their deletion, and the last four revisions of a file are kept as well. This means that if you discover a file is corrupted, and it's been changed three or less times, we can probably recover a version of the file before it was corrupted.

NOTE:

To give the best chance that we can recover a file for you, you MUST send email to help@astro as soon as you realize you need a file recovered! The longer you wait, the less chance there is that we can get the file back.

Recovering files via TSM

Due to the way TSM operates, you cannot restore your own files that were on the home directory server. We will have to run the restore for you. Please email help@astro as soon as you realize you need a file restored so we have a better chance of recovering it for you.