Department of Computer Science and Technology

Retrieving lost data

For every directory that is maintained on the filer, data about old files is maintained, with new data compiled every hour. The data is organised as directories which contain your files as they were at the time the snapshot was taken. Each directory on the file server therefore contains a directory whose name is .snapshot (under Unix), or ~snapshot (under Windows).

Using snapshots

You have to navigate to snapshot directories manually as they do not appear in directory listings or Windows folder displays, and do not respond to filename completion (under Unix). In Windows, snapshots will be shown as separate folders in the ~snapshot folder. Under Unix, using ls -lu in the .snapshot directory will return a list similar to this one:

drwxr-xr-x 113 ckh11 ckh11 49152 Mar 19 00:00 sv_daily.0
drwxr-xr-x 113 ckh11 ckh11 49152 Mar 17 00:00 sv_daily.1
drwxr-xr-x 113 ckh11 ckh11 49152 Mar 16 00:00 sv_daily.2
drwxr-xr-x 113 ckh11 ckh11 49152 Mar 15 00:00 sv_daily.3

If you require a snapshot that is older than the main ones you can see, and which are likely to be available elsewhere, contact the sys-admin, who may be able to help.

Even though you own the snapshot directories, you can't write to them or mv (under Unix)/cut and paste (under Windows) files from them. Because of that, retrieving files from a snapshot must always be a "copy" operation.

System backup

The file server is remarkably resilient and very unlikely to lose your files. However, just in case something does happen to your files while they are stored on the file server, or if you mistakenly delete one of your own files and not realise it until after the last snapshot copy of it has disappeared, we store further snapshots on our secondary filer.

To ask for a file to be retrieved, mail a request to sys-admin with details of:

  • the file name;
  • the file's path;
  • the date the file was lost.