Patent ID: 8635424

Claim:
A storage system in which first and second storage control devices are connected to each other for communications, the system comprising: a first volume that is provided virtually to the first storage control device; a second volume that is provided virtually to the second storage control device with correspondence in terms of a storage space with the first volume, and is accessed in response to an access request to the first volume; a pool section that keeps a plurality of physical storage areas for allocation to the second volume in response to a write access request to the second volume; a first control section that is provided to the first storage control device issues a command to the second volume in response to the access request to the first volume, and performs data reading/writing from/to the second volume; and a second control section that is provided to the second storage control device, performs data input/output to/from the second volume in response to the command from the first control section, and allocates, to the second volume, in response to a write access request from the first control section, any of the plurality of physical storage areas in the pool section not yet in use, and wherein the first control section includes first management information for use to manage a state of use of areas in the first volume and second management information for use to manage a state of use of areas in the second volume, and wherein the first and second management information each include information about whether the areas are each written with data.