To ensure the consistency of data included in blocks which have already been received and has already been remote-copied, on a file basis, in a destination NAS system, when remote copy has failed due to a failure which has occurred in a source NAS system, there is provided a method in which: a source NAS system transmits a correspondence between an updated block and a file, to a destination NAS system when remote copy is started; the destination NAS system records a remote copy state for each block; a management server refers to the information recorded by the destination NAS system and selects files from which all the update blocks have been received, when remote copy has failed due to a failure which has occurred in the source NAS system; and the destination NAS system stores data included in the update blocks of the files selected by the management server.