For betterment, by putting a virtual storage device into a suspend mode, physical resources are turned OFF on a virtual storage device basis. Moreover, control information and volume data of the virtual storage device are stored in any external volume, for example, and the resources that have been used by the virtual storage device are deallocated. At the time of resumption of operation, using any resources not in use, the virtual storage device is restored based on the control information in storage. When a change is made to a WWN on the side of a host, the storage device receives a WWN change notification from a management server, and makes settings again to a WWN table, thereby making it accessible from the host.