Patent ID: 7404051

Claim:
A method of creating in a second storage system a replica of a snapshot volume in a first storage system, the method comprising the steps of: providing a primary volume (P-VOL) at the first storage system, wherein the P-VOL contains data; providing a differential volume (D-VOL) at the first storage system, wherein the D-VOL contains data copied from files or blocks that were on the P-VOL prior to the files or blocks being changed on the P-VOL following each predetermined point in time that a snapshot is taken; storing mapping information of the P-VOL and the D-VOL in a first snapshot volume management table at the first storage system; designating a first target volume in the second storage system for receiving replication of the P-VOL, and a second target volume in the second storage system for receiving replication of the D-VOL; storing transfer information including the mapping information of the P-VOL and the D-VOL and information of the first and second target volumes in a copy pair management table at the first storage system; commencing replication of the P-VOL from the first storage system to the first target volume in the second storage system; commencing replication of the D-VOL from the first storage system to the second target volume in the second storage system; sending the transfer information to the second storage system; and creating a replica snapshot volume in the second storage system from the first target volume and the second target volume, as identified from the transfer information.