Patent ID: 8266377

Claim:
A storage system comprising: a first storage apparatus, coupled to a host computer, including first volumes; a second storage apparatus, including second volumes corresponding to the first volumes and managing a first pair between the first volumes and the second volumes, for storing replication data of the first volumes to the second volumes by first remote copy; and a third storage apparatus, including third volumes corresponding to the first volumes and managing a second pair between the first volumes and the third volumes, for storing replication data of the first volumes to the third volumes by second remote copy, wherein the second storage apparatus is configured to manage a third pair between the second volumes and the third volumes, wherein the second storage apparatus is configured to judge whether or not an amount of the second volumes and another amount of the third volumes are identical with each other when the second storage apparatus receives, from the host computer, a reservation instruction for transferring differential data showing a difference between each of data of the second and third volumes to the third volume during a remote copying operation at each of the first and the second pairs, and wherein the second storage apparatus is further configured to determine whether it is possible to perform the second remote copy at the third pair, and also configured not to transfer the differential data until an instruction for transfer reaches the second storage apparatus.