Patent ID: 7281099

Claim:
A clustered storage system comprising: a first storage system having a first memory and a plurality of first disk drives, said first memory including first volume pair information, wherein said first volume pair information comprises a first pair information table and a first volume information table; a second storage system having a second memory and a plurality of second disk drives, said second memory including second volume pair information, wherein said second volume pair information comprises a second pair information table and a second volume information table; and a network connecting between said first and second storage systems, wherein said first pair information table contains information regarding a pair related to said first storage system and said second pair information table contains information regarding a pair related to said second pair information table, wherein said first volume information table contains information regarding all of the volumes contained in said first storage system and said second volume information table contains information regarding all the volumes contained in said second storage system, wherein each of said first storage system and said second storage system has access to both of said first volume pair information and said second volume pair information via said network, wherein said first storage system sends data stored in said plurality of first disk drives to said second storage system via said network, wherein said second storage system stores data sent from said first storage system into said second memory, wherein said first storage system instructs said second storage system to transfer said data from said second memory to said plurality of second disk drives, and wherein said second storage system transfers said data from said second memory to said plurality of second disk drives based on said instruction.