A storage device (1) communicating with a host computer and other storage devices through a network is characterized in that the storage device (1) secures memory buffers for temporarily storing data in a remote copy operation carried out between the storage devices. A network memory (100) in the storage device (1) includes an available buffer comprising a plurality of memory buffers and an in-use buffer also comprising a plurality of memory buffers. A buffer control unit (215) secures memory buffers of the available buffer as a reserved buffer having a reserved-buffer size specified in a buffer reservation request made by a storage management device (8) in response to the request. The buffer control unit (215) then allocates the memory buffers of the reserved buffer as the in-use buffer in response to a request received from the storage management device (8) to start a remote copy operation.