Patent ID: 8032726

Claim:
A system comprising: a plurality of first storage devices each connected to a host computer; and a plurality of second storage devices each connected to any of the first storage devices, wherein each of said plurality of first storage devices is configured to defer processing of a write request received from the host computer based on an instruction from a management unit and to restart thereafter processing of the write request received from the host computer based on the instruction from said management unit; wherein each of said plurality of first storage devices is configured to manage as a write data set write data of the write request processed after processing of the write request has been restarted according to the instruction from said management unit until processing of the write request is deferred according to an instruction from said management unit; wherein said management unit is configured to receive a completion report of deferring processing of the write request from said plurality of first storage devices and then to instruct said plurality of first storage devices to create new write data sets, to attach common identification information to the write data set created in said plurality of first storage devices, and then to instruct said plurality of first storage devices to restart the processing of the write request; wherein each of said plurality of second storage devices is configured to store the write data received from the first storage device for each write data set in logical volumes of said second storage devices and said plurality of second storage devices store the write data of the write data set having the same identification information in logical volumes of said second storage devices based on the instruction from said management unit; wherein said management unit is configured to receive a completion report of deferring the processing of the write request from said plurality of first storage devices and then to instruct said plurality of first storage devices to send the write data to any of said plurality of second storage devices with respect to a write data set containing the write data of the write request processed by each of the plurality of first storage devices before the deferring of the processing of said write request is executed; wherein each of said plurality of second storage devices has a cache memory and is configured to store the write data received from any of the first storage devices in said cache memory; wherein said management unit, after said plurality of first storage devices have completed sending the write data relating to said write data set, instructs said plurality of second storage devices to store the write data of said write data set stored in said cache memory in logical volumes of the second storage devices; and wherein any of said plurality of first storage devices has said management unit.