Patent ID: 6973553

Claim:
A data storage system, comprising: a host computer system; a first set of storage volumes; a second set of storage volumes for backing-up data from the first set of storage volumes; and a controller for controlling the transfer of data from the host system to the first and second set of storage volumes, wherein at least the first set of storage volumes further comprises data recording media including a plurality of extended format sectors, the extended format sectors comprising a user data sector field for storing user data and a backup indicator field for indicating the status of the user data sector field; wherein the backup indicator field indicates whether the user data in the user data sector field has been written to backup storage subsequent to a previous backup operation and wherein the first set of storage volumes is arranged as a virtual space wherein the host views the configuration as being a storage device having a first predetermined size and the controller allocates storage space from the first set of storage volumes having a physically smaller size than viewed by the host.