A storage system comprises a primary storage device having a primary storage area, a first secondary storage device having a first secondary storage area, and a second secondary storage device having a second secondary storage area. Responsive to host request from a host computer, the primary storage device writes requested host data to the primary storage area. Furthermore the primary storage device sends 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 first and second copy request containing the copy data which is a copy of the host data. Here the second secondary storage area is identified by a virtual identifier used to identify the second secondary storage area as the virtual storage area within the primary storage device.