Patent ID: 7360046

Claim:
A storage system having a first storage device connected to a host system and which provides a first volume for storing data transmitted from said host system, and a second storage device connected to said first storage device and which provides a second volume for storing backup data of said first volume; wherein said first storage device comprises a journal creation unit for creating a journal representing the written contents when said data is written in said first volume; said second storage device comprises: a snapshot acquisition unit for acquiring a snapshot of said second volume in a prescribed timing; a memory device for storing each of said journals transmitted from said first storage device and said snapshot acquired with said snapshot acquisition unit; a volume rebuilding unit for rebuilding, upon using the corresponding said journal and said snapshot stored in said memory device in accordance with the rebuilding order designating the rebuilding time provided from said host system, said first volume at said rebuilding time; and a difference data output unit for outputting said data of an address rewritten from said rebuilding time onward among said rebuilt data stored in said first volume at said rebuilding time as difference data; and said first storage device rebuilds said first volume at said rebuilding time based on said difference data transmitted from said second storage device.