Abstract: An improved backup storage system and method for use in conjunction with hierarchical or mass storage servers and networks is disclosed. Baseline, full and incremental backup procedures are used to save file copies. In one preferred embodiment, the baseline backup procedure is used to store copies of stable files, i.e. files that are modified less frequently, if at all. With a hierarchical storage server, such files are typically those stored on tertiary storage media, e.g. erasable optical disks, WORMs or magnetic tape. The full backup procedure stores, as full backup copies, copies of all files not in the baseline backup and files that have been changed since the time of their baseline backup. The full backup procedure also stores file identifiers and signal representative of storage locations of baseline backup copies for files which have not been changed since the time of the baseline backup.