In remote data replication between storage systems, there are cases where the storage extent capacity used as the temporary storage extent in the storage system will incur waste. In a system having a management computer, a host computer, a first storage system, and a second storage system, when maintaining the replicated data of the first storage system in the second storage system via remote data replication, a change or the like in the traffic from the host computer to the first storage system is monitored, and the management computer instructs the storage system to switch the remote data replication mode in accordance with such traffic.