Patent ID: 7334155

Claim:
A method for a remote copy system which comprises: a first computer; a plurality of first storage systems connected to said first computer; a second computer; and a plurality of second storage systems connected to a second computer; wherein: each of said plurality of first storage systems comprises a first storage unit and a first storage control unit connected to said first storage unit; each of said plurality of second storage systems comprises a second storage unit and a second storage control unit connected to said second storage unit; each of said plurality of first storage systems is coupled to one of said plurality of second storage systems, the method comprising the steps of: on a side of said first storage control unit, receiving a plurality of write requests including write times from said first computer, writing write data in each write request in said first storage unit in an order of the write request having an older write time, transmitting a completion of a write process to said first computer, and transmitting the write requests to said second storage control unit connected to said first storage control unit in an order of an older write time; on a side of said second storage control unit, receiving the write requests from said first storage control unit connected to said second storage unit, storing the write requests in a secondary update information storage unit possessed by said second storage control unit in the order of the older write time, and transmitting a completion report to said first storage control unit connected to said second storage control unit; on a side of said second computer, determining a standard time to be used for said second storage control unit to determine whether the write data in each write request is stored in said second storage unit, and also determining a subsidiary standard time which is the latest time from all times reported from all of the second storage systems when the standard time is determined; on the side of said second storage control unit, writing the write data in each write request having a write time equal to or before said standard time; inquiring to said first storage control unit as to whether it has received a new write request from the first computer, and, if the second storage control unit receives a notice from said first storage control unit which notice indicates that said first storage control unit did not receive a new write request from the first computer, sending the subsidiary standard time to said second computer, so that said second computer can update the standard time.