System for backing up computer disk volumes

A system for backing up data from a computer disk volume at very high speed by saving a logical image copy of the volume to a backup medium such as magnetic tape. This logical image copy can later be restored in its entirety to a disk volume with a different physical geometry and flaw map in a disaster recovery mode, significantly reducing the time required for such disaster recovery compared to other backup techniques. In addition, the logical image copy on the backup medium also allows selective file restore with performance comparable to that achievable using traditional file-by-file backup/restore methods. The backup process can thus run considerably faster than conventional approaches without sacrificing the restore flexibility normally associated with those approaches.