Patent ID: 7219202

Claim:
A storage system coupled to a host computer comprising: a plurality of control units each connected with a respective disk unit and controlled to read/write data sent from the host computer from/to the respective disk unit, each of the plurality of the control units including a replication creation unit being adapted to create a replication of the data of a logical volume relating to the disk unit connected with the corresponding control unit; and a plurality of volume pair information corresponding to the plurality of the control units, respectively, each of the volume pair information designating an original volume and a replication volume, wherein the replication creation unit of a first control unit operates in such a manner that in the case where a replication of an original volume, relating to the disk unit connected to the first control unit, is created in the logical volume relating to the disk unit connected to the first control unit, the volume information of the original volume and the volume information of the replication volume are registered in the volume pair information, and the replication is created in the logical volume relating to the disk unit connected to the first control unit based on the volume pair information, and in the case where a replication of an original volume, relating to the disk unit connected to the first control unit, is created in a logical volume relating to the disk unit connected to a second control unit, the volume information of the original volume, virtual volume information of a virtual replication volume virtualized in the disk unit connected to the first control unit, and information on the second control unit are registered in the volume pair information, and a request to create a replication is transmitted to the second control unit based on the volume pair information when a replication request is sent from the host computer for creating the replication volume in the disk unit connected to the first control unit, wherein the virtual volume information of the virtual replication volume includes a volume number of a volume virtualized in the disk unit connected to the first control unit but for which no volume is created in the disk unit connected to the first control unit, and wherein the host computer recognizes the replication volume created in the logical volume relating to the disk unit connected to the second control unit as having been created in the logical volume relating to the disk unit connected to the first control unit; and wherein, in the case where the replication volume is created in the logical volume relating to the disk unit connected to the second control unit, a replication data of the original logical volume is transferred from the first control unit to the at least one logical volume of the second logical unit based on the volume pair information.