Patent ID: 7721058

Claim:
A storage system comprising: a plurality of protocol converting adapters each adapted to be coupled to a host computer and to convert a protocol of a command received from the host computer; an internal network coupled to the plurality of converting adapters; and a plurality of control units, each coupled to the internal network, and each comprising at least one processor and each controlling to cache data transferred between one of the plurality of protocol converting adapters and the host computer and each executing a Redundant Array of Inexpensive Disks (RAID) control for a plurality of disk units; wherein a first protocol converting adapter of said plurality of protocol converting adapters selects a control unit of the plurality of control units based on said command received from the host computer; said first protocol converting adapter sends said converted command, of which a protocol is converted, to said selected control unit of the plurality of control units, which controls a volume storing data requested by the converted command; the plurality of control units includes a first control unit and a second control unit; the plurality of disk units includes a first disk unit and a second disk unit; the first control unit is coupled to the first disk unit and configured to perform a read/write in response to a request sent from the host computer with respect to the first disk unit; the second control unit is coupled to the second disk unit and configured to perform read/write in response to a request sent from the host computer with respect to the second disk unit, the first control unit forms a pair relationship between a first volume in the first disk unit and a second volume, the second volume being a virtual volume related to a third volume in the second disk unit, and the first and second control units control copying between the first volume in the first disk unit and the third volume in the second disk unit according to a copy request specifying the first and second volumes from the host computer.