Patent ID: 7783848

Claim:
A storage system being adapted to be coupled to a first host computer and a second host computer via a network comprising: a first data volume storing write data from the first host computer, the first data volume being associated with a first journal group to which an order of write operations from the first host computer is guaranteed; a second data volume storing write data from the second host computer, the second data volume being associated with a second journal group to which an order of write operations from the second host computer is guaranteed; snapshot storing areas storing at least one snapshot of at least a portion of each of the first and second data volumes; a first journal storing area storing journal entries associated with write data to the first journal group; and a second journal storing area storing journal entries associated with write data to the second journal group; wherein the first journal storing area is configured to permit data recovery within a first determined range by using said at least one snapshot of at least a portion of the first data volume and a portion of the journal entries stored in the first journal storing area, wherein the second journal storing area is configured to permit data recovery within a second determined range by using said at least one snapshot of at least a portion of the second data volume and a portion of the journal entries stored in the second journal storing area, wherein in order to recover data of a portion of the first or second data volume at a specific point in time within the first or second determined range, the storage system recovers the data of the portion of the first or second data volume at the specific point in time, and wherein the storage system releases at least one of the stored journal entries from the first or second journal storing areas based on the configuration of the first and second journal storing areas while permitting data recovery within the first and second determined ranges.