Patent ID: 7698374

Claim:
A storage system comprising: a first storage area for storing data; a second storage area for storing data; a first storage control unit configured to control the first storage area; and a second storage control unit configured to control the second storage area, wherein, a first host computer is coupled to the first storage control unit and a second host computer is coupled to the second storage control unit, copy processing is performed to copy data stored in the first storage area into the second storage area, thereby creating a copy pair including the first storage area and the second storage area, when the first storage area and the second storage area are in a copy-pair state, in response to a first write request sent from the first host computer to write data in the first storage area, the first storage control unit writes data in the first storage area and transfers the first write request to the second storage control unit, the second storage control unit includes: a third storage area, which is used when transferring a write request from the second host computer to write data in the second storage area to the first storage control unit; and memory including a management information storing area that stores management information for the copy pair and is used to manage the third storage area, wherein the second storage control unit writes the data in the second storage area in response to the first write request transferred from the first storage control unit, applies a second write request sent from the second host computer to write data in the second storage area to the third storage area, and transfers the second write request to the first storage control unit based on the management information, the first storage control unit writes data in the first storage area in response to the second write request transferred from the second storage control unit and transfers the second write request back to the second storage control unit, and the second storage control unit writes the data in the second storage area in response to the second write request transferred from the first storage control unit.