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Backups and mirrors
As a matter of routine, we backup and mirror all user home directories. We do this for most group space too. We can also do the same for self-managed machines.
By "mirrors" we mean copies of data taken and stored on disk in an off-site location (ie not in the same part of town). These copies are usually taken once a night. They have the benefit of being nearly instantly available, but there's no history. So you can't use them to return your data to the state it was say last week, only to as it was when the last mirror was taken.
To mirror machines, we use rsync to copy the data off.
We use AFS's "sites" feature to keep off-site copies of AFS volumes.
By "backups" we mean a copy of data made to tape. Again, this copy is off-site (Kings Buildings) and we take them nightly. Tape is slower to copy and restore data than mirroring, but does have the advantage of keeping 6 months worth of daily backups, and 13 months of monthly backups. So you can go back in time to restore things as they were up to a year ago, but with increasing granularity. But after 13 months those tapes are recycled, so data older than that cannot be restored.
We use a commercial product, TiBS, to backup both machines and AFS data.
Users of self-managed machines can also use our backup server to backup a maximum of 5G of their data. See the self-managed backups topic for details.
If you have a large amount of data that you would like mirrored or backed up to tape, then the basic charge is £250 per 500GB for either a mirror or backup. So for us to mirror and backup 1TB of data, the cost to you would be:
2x£250 (mirror) + 2x£250 (backup) = £1000.
However, we will not charge for mirrors up to 200GB, nor for tape backup to 200GB.
If you have deleted a file from your home directory within the last 24 hours, you should find it in the directory called Yesterday within your home directory. The Yesterday directory is created nightly and is a copy of the contents of your home directory from the day before. If you don't find the file you are looking for, contact support and tell us, as accurately as you can:
- the names of the files
- which directory they were in
- roughly what date you want the files back from
Please try to backup important data and other items yourself in the first instance, so you do not need to rely on us. We cannot always guarantee full restoration of what you have lost.
Data stored locally on your DICE machine (e.g. in /disk/scratch) is NOT routinely backed up. It should therefore only be used for transient data or data that is easily reproducible.