Patent ID: 7594086

Claim:
A storage system for providing a host computer with a data storage area, comprising: a primary storage device connected to the host computer and having a primary storage area for the host computer; a first secondary storage device connected to the primary storage device and having a first secondary storage area; and a second secondary storage device connected to the primary storage device and having a second secondary storage area, the primary storage device comprising: a virtualization unit configured to set a correlation between the second secondary storage area and a virtual identifier used to identify the second secondary storage area as a virtual storage area within the primary storage device; a primary writing unit configured to execute a primary write process, the primary write process including a process of receiving from the host computer a host request which is a data write request of host data, and a process of writing the host data to the primary storage area; and a copy control unit configured to send a first and second copy request to the first and second secondary storage devices, respectively, to store copy data in the first and second secondary storage areas, the copy data being a copy of the host data, the first and second copy request containing the copy data, wherein the copy control unit, regardless of whether or not receiving a completion notification of the second copy request from the second secondary storage device, sends a completion notification of the host request to the host computer responsive to receiving a completion notification of the first copy request from the first secondary storage device, and the copy control unit identifies the second secondary storage area using the virtual identifier in the second copy request; wherein the copy control unit comprises: a copy instruction unit configured to create the first and second copy request, the copy instruction unit creating the second copy request identifying the second secondary storage area using the virtual identifier; and an access control unit configured to send the first and second copy requests to the first and second secondary storage devices, respectively, wherein, the access control unit, by referencing the correlation set by the virtualization unit, replaces the virtual identifier within the second copy request with an actual identifier of the second secondary storage area, and sends the second copy request after the replacement to the second secondary storage device.