The first facility is the backup volume, which you create by cloning a read/write volume. The backup volume is read-only and so preserves the state of the read/write volume at the time the clone is made.

Backup volumes can ease administration if you mount them in the file system and make their contents available to users. For example, it often makes sense to mount the backup version of each user volume as a subdirectory of the user's home directory. A conventional name for this mount point is OldFiles. Create a new version of the backup volume (that is, reclone the read/write) once a day to capture any changes that were made since the previous backup. If a user accidentally removes or changes data, the user can restore it from the backup volume, rather than having to ask you to restore it.

The OpenAFS User Guide does not mention backup volumes, so regular users do not know about them if you decide not to use them. This implies that if you do make backup versions of user volumes, you need to tell your users about how the backup works and where you have mounted it.

Users are often concerned that the data in a backup volume counts against their volume quota and some of them even want to remove the OldFiles mount point. It does not, because the backup volume is a separate volume. The only amount of space it uses in the user's volume is the amount needed for the mount point, which is about the same as the amount needed for a standard directory element.

Backup volumes are discussed in detail in Creating Backup Volumes.

Backup volumes can reduce restoration requests, but they reside on disk and so do not protect data from loss due to hardware failure. Like any file system, AFS is vulnerable to this sort of data loss.

To protect your cell's users from permanent loss of data, you are strongly urged to back up your file system to tape on a regular and frequent schedule. The AFS Backup System is available to ease the administration and performance of backups. For detailed information about the AFS Backup System, see Configuring the AFS Backup System and Backing Up and Restoring AFS Data.