In a storage system that executes multi-target remote copying, the identity of data across two secondary storage subsystems may be quickly and flexibly ensured. The storage system includes a first storage subsystem that has a first storage area and multiple second storage subsystems that each have a second storage area to store duplicate data for data stored in the first storage area. In this storage system, a write process that writes write data to the first storage area is executed. In response to the write process, the write data is copied to the second storage area of each second storage subsystem. Furthermore, a write section that the copy information belongs to, wherein the copy information that corresponds to the write process, is determined for each write process. In addition, history information regarding each executed copy operation is created for each write section to which the copy information used for such operation belongs.