Astrophysics Research CentreQueen's University Belfast • School of Mathematics & Physics |
Automatic system backupsThis page gives information on the backups of user data that are made automatically - these are, of course, merely in addition to a regular personal backup schedule! Home areas
All users have two areas on their PCs where they may store files. The home area (found in /home/user/ where user is your username) is relatively small (about 500 hundred megabytes), and files there are backed up nightly on the central servers. Copies are also taken offsite on tape in case of disaster. This area should be used for (relatively small) files of critical importance, such as reduced datasets, papers, theses, email, etc. Note that not all files in the home area are backed up. For efficiency, certain unimportant files are not saved, for example, web browser cache files, and core-dump files.
Scratch areas
We now make backups of some scratch areas each night as well. These are stored on a 2TB RAID5 array. Not all scratch areas are backed up - there is a limit of 1 scratch area per user (eg /scratch/rsir is backed up, /scratch/rsir2 is not). As with the home area backups, we currently keep a weeks worth of backups online at a time. Weekly dumps to tape are also made in case of disaster, and several weeks worth of tapes are kept offsite for security. As with the home area backups the scratch area is imaged each night around 10PM.
Given the size of scratch areas - tens of GB - some limits have to be placed on what can be backed up centrally. On a practical level, we can assign a notional 50GB of space per user on the backup RAID, however if all users were to use all 50GB then the array would overflow. So don't keep archive data online - write it out to tape or DVD! When we do arrive at the point where the RAID is overfull then either the frequency of the backups will be reduced (to, say, Mon, Wed, Fri only), or the heaviest users will be removed from the automated backups and will have to make their own arrangements - the needs of the many outweigh the needs of the few, etc.
Restoring files from backup
The advantage of these systems is that users can restore files themselves without calling on the systems administrator. Duplicate home areas are held in /backups/homes/DayXX/machine/user/ where machine is the name of your workstation (eg. dax, picard, mozart, etc), dayXX is Mon10, Tue11, etc, and user is your user id. Simply copy the deleted files using the normal cp command.
Similarly, the scratch backups are available as /backups/scratch/DayXX/user/.
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