Patent ID: 8037027

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 physical storage device for storing data; and a first controller for controlling writing and reading of data to/from the physical storage device, the first storage system managing a storage area of the 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 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 physical storage device, the second storage system managing a storage area of the 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 logical volume, wherein: the first storage system transmits the journal data including the first differential data item to the second storage system; the second storage system stores the journal data received from the first storage system into the third logical volume; the first storage system deletes at least the first differential data item from the second logical volume; the computer system retains a first management information set that includes information for associating the first logical volume with the third logical volume storing therein the journal data including the first differential data item related to the first logical volume, the journal data related to the first logical volume further includes a second differential data item representing a differential between the data that was stored in the first logical volume at the second time instant and data that was stored in the first logical volume at a third time instant being later than the second time instant; and the first storage system is configured to: create, based on the first differential data item and the second differential data item, a third differential data item representing a differential between the data that was stored in the first logical volume at the first time instant and the data that was stored in the first logical volume at the third time instant; and transmit the journal data including the created third differential data item to the second storage system.