Patent ID: 7757114

Claim:
A remote copy system, comprising: a first storage system including a first storage controller and a first data volume, the first storage controller being configured to receive a write request from a first host associated with the first storage system and to store a write data associated with the write request to the first data volume; a second storage system coupled to the first storage system, including a second storage controller and a second data volume, the second storage controller receiving first data containing the write data to copy the stored data in the first data volume to the second data volume; and a third storage system coupled to the second storage system, including a third storage controller and a third data volume, the third storage controller receiving second data containing the write data to copy the stored data in the first data volume to the third data volume, wherein the second storage system manages a first status information indicating whether a corresponding data to the write data received at the second storage system is necessary to be transmitted from the first storage system to the third storage system, wherein the third storage system manages a second status information indicating whether data is changed on the third storage volume, wherein the second storage system and the third storage system synchronize the second data volume and the third data volume by using the first status information and the second status information when the first storage system experiences failure, wherein the second storage system and the third storage system synchronize the second data volume and the third data volume by exchanging a differential data between the second data volume and the third data volume.