Patent ID: 8131963

Claim:
A remote copy system comprising: a plurality of primary storage systems, wherein each of the plurality of primary storage systems comprises a first controller and a source logical volume coupled to said first controller; and a plurality of secondary storage systems, wherein each of the plurality of secondary storage systems comprises a second controller, a memory, a cache memory, and a target logical volume storing copy data of said source logical volume, wherein the first controller of each of said primary storage systems comprises: a write-data receiving unit that receives write data from a host computer and creates, for the write data received from the host computer, write-data management information including sequential numbers and section numbers, the sequential numbers being based on an order of receiving the write data; a write-data transfer unit that creates write data information with reference to the write-data management information, and sends to one of said plurality of secondary storage systems the write data and corresponding write-data information, which includes the sequential numbers and the section numbers, wherein management software is executed in the first controller of one of said plurality of primary storage systems, and said management software reads the section numbers stored in a control memory of each of said primary storage systems, selects a section number having a smallest value among the read section numbers, and sends the selected section number to a write-data reflecting unit of each of said plurality of secondary storage systems.