Patent ID: 7600089

Claim:
A primary disk controller being configured to be coupled to at least one host computer and a plurality of first disk devices and being configured to receive a first plurality of data sent from the a host computer, the primary disk controller comprising: one or more data control sections; and a first cache memory, wherein the one or more data control sections manage a plurality of sequence information, each of which is provided to one of the first plurality of data in a received order by the primary disk controller, and manage overwrite information, which is increased, if two or more of the first plurality of data are to be written to a common record during a time period, the one or more data control sections, if the two or more of the first plurality of data are to be written to the common record during the time period, manage a latest update data, which is a latest data overwritten to the common record during the time period, and write a second plurality of data, which include the latest update data and one or more data other than data to be updated by the latest update data, to at least one of an area of the first cache memory and an area of the first plurality of disk devices, and transfer the second plurality of data to a secondary disk controller by the remote copy process, so that the secondary disk controller receives one or more of the second plurality of data from the primary disk controller, and verifies whether a set of the second plurality of data is received based on the plurality of sequence information, the overwrite information and a sequence information of data to be received during a subsequent time period of the time period, and writes the second plurality of data to an area of a second cache memory of the secondary disk controller based on the plurality of sequence information, if the set of the second plurality of data is received.