Provided is a storage system having a first storage controller and a second storage controller. An actual device of the second storage controller is mapped to a virtual device of the first storage controller. The first storage controller has a port for transmitting control cylinder information to be written in a control information area of the actual device. As the format data to be transmitted from the first storage controller to the second storage controller, it will suffice so as long as control cylinder information is transmitted, and high speed formatting can be performed since it is not necessary to transmit 0 data.