In a system in which data employed by a computer is stored in a storage system, the storage system transfers this data to another storage system and a copy of the data is maintained in the other storage system, consistency of the copy is maintained even in the case of data written to the storage system by a computer, to which a write time is not applied.A source storage system, when a write time is applied to a write request, records the write time and applies this write time to the received write data and, when no write time is applied, applies the recorded write time to the received write data and transfers the write data with this write time applied thereto, to another storage system. The target storage system stores the write data in a logical volume in the target storage system in accordance with the write time.