ABSTRACT
As disk systems were developed, the sequential nature of tape forced it into the realms of backup, hierarchical storage management and archive. Simply put, tape could not compete effectively with high-speed random access to active data offered by hard disk systems. Particularly when moving data to tape, the goal would always be to ensure that by the time data was relocated from disk to tape, it was old and had not been accessed for some time. By allowing backups to span over as many tapes as required to ensure the data is backed up, enterprise products avoided tape wastage and reduced the potential for human error preventing key data from being backed up. Tape-level multiplexing can be essential to keep tape drives streaming at optimum speed but, depending on the level of multiplexing and the type of recovery that is required, can have a deleterious effect on the most important component of a backup system—the recovery.
