Patent ID: 8397041

Claim:
A storage system connected to one or more host computers, comprising: a plurality of storage devices connected to the one or more host computers, wherein at least one of the plurality of storage devices comprises a first controller, wherein another one of the plurality of storage devices comprises a second controller, and wherein the plurality of storage devices comprises: a control memory; a cache memory that temporarily stores write data received from the one or more host computers; and one or more logical volumes that store the write data stored in the cache memory, wherein the first controller comprises: an update command unit that commands an update of a section number stored in the control memory of the plurality of storage devices, and wherein the second controller comprises: a write-data receiving unit that receives a write request and the write data from the one or more host computers, and stores the received write data in the cache memory, and generates write-data management information including a sequential-number and the updated section number stored in the control memory, the sequential number being based on an order of receiving the write data; and a section number generating unit that updates a value of the section number according to the update command for the section number, and stores the updated section number in the control memory, wherein the update command unit of the first controller issues a hold command to the second controller, wherein the write-data receiving unit of the second controller puts processing of the write request received from the one or more host computers on hold when the hold command is received, and reports completion of hold to the update command unit, wherein the update command unit of the first controller issues the update command for the section number to the second controller when the report of the completion of hold is received from the second controller, wherein the section number generating unit of the second controller updates the value of the section number to a value included in the update command when the update command is received, and reports completion of update to the update command unit, wherein the update command unit of the first controller issues a hold cancel command to the second controller when the report of the completion of update is received from the second controller, and wherein the write-data receiving unit of the second controller cancels the hold on the processing of the write request received from the one or more host computers when the hold cancel command is received.