Patent ID: 7606990

Claim:
A storage system comprising: a disk device which comprises: an original volume for storing data which is read/written by a host; and a snapshot volume for storing snapshot data of a plurality of snapshot generations of the original volume; and a storage control unit which comprises: a management unit for managing the storage control unit; a channel I/F that is connected to the host; and a device I/F that is connected to the disk device, characterized in that: the disk device further comprises a copy volume for storing a copy of the original volume at a predetermined timing, the snapshot volume is arranged to provide each of said plurality of snapshot generations to the host as a virtual volume and to store data having an identical content in one storage area, and in that the management unit is arranged to: determine, when the host sends a request to create the original volume as a new volume of a designated generation, whether the designated generation is a generation of the copy volume or not; overwrite data in the copy volume for a block address of the designated generation indicating the snapshot volume if the generation of the copy volume is different from the designated generation; and change mapping information of the copy volume to the mapping information of the original volume.