A method for controlling a storage system having first and second switches and a storage device connected to the switches via a network in response to a request from a host, the storage device having first and second areas, each of the first and second switch accessing to the first and second area, the method includes, receiving a request for copying data stored in the first area to the second area from the host, transmitting initiation notification of the copying to the second switch, executing the copying by the first switch, maintaining progress status of the copying, controlling the second switch to refer to the progress upon receiving a request for access to the first or second area by the host before completion of the copying, and determining whether to permit access to the first or second area by the second switch.