Patent ID: 7272693

Claim:
A storage system connected to a host computer comprising a first disk array device and a second disk array device mutually connected, wherein ( 1 ) said first disk array device comprises: a first volume; a first withdrawal volume for storing data withdrawn from said first volume; a generational management control section for generating generational management data which record the storage contents of said first volume at a prescribed point in time, in the form of differential data, and for managing generations of back-up data in said first volume; a first storing section for storing said generational management data generated by said generational management control section; a generational management data transferring section for transferring said generational management data stored in said first storing section to said second disk array device; and a volume transferring section for respectively transferring the storage contents of said first volume and said first withdrawal volume, to said second disk array device, said volume transferring section and said generational management data transferring section transferring respective data substantially simultaneously; and ( 2 ) said second disk array device comprises: a second volume to which the storage contents of said first volume received from said volume transferring section are copied; a second withdrawal volume to which the storage contents of said first withdrawal volume received from said volume transferring section are copied; and a generational management data duplicating section which causes said generational management data received from said generational management data transferring section to be copied to a second storing section, wherein the first disk array device backs-up to the second disk array device the first volume of only one designated generation on the basis of an instruction from the host computer to be restored thereafter, and the second disk array device restores the first volume of said only one designated generation on the basis of an instruction from the host computer.