Patent ID: 8260746

Claim:
A computer system, comprising: a first storage system coupled to a network; and a second storage system coupled to the first storage system, the first storage system comprising: a first physical storage device for storing data; and a first controller for controlling writing and reading of data to/from the first physical storage device, the first storage system managing a storage area of the first physical storage device within the first storage system as a plurality of logical volumes, the plurality of logical volumes within the first storage system including a first logical volume and a second logical volume, the second logical volume storing therein journal data related to the first logical volume, the journal data related to the first logical volume including a first differential data item representing a differential between data that was stored in the first logical volume at a first time instant and data that was stored in the first logical volume at a second time instant being later than the first time instant, the second storage system comprising: a second physical storage device for storing data; and a second controller coupled to the first storage system, for controlling writing and reading of data to/from the second physical storage device, the second storage system managing a storage area of the second physical storage device within the second storage system as a plurality of logical volumes, the plurality of logical volumes within the second storage system including a third and fourth logical volume, wherein: the first storage system being transfigured to transmit the copy of the journal data including the first differential data item and the data stored in the first volume at the second time instance to the second storage system; the second storage system being transfigured to store the copy of the journal data received from the first storage system into the third logical volume; the second storage system being transfigured to store the copy of data stored in the first volume received from the first storage system into the fourth logical volume, and to delete at least the first differential data item from the second logical volume; and wherein the journal data stored in the third logical volume includes the information managing the pair of the copy of the journal data stored in the third logical volume and the copy of data stored in the forth logical volume.