Patent ID: 8078809

Claim:
A storage system comprising: a controller coupled to a host computer; a plurality of disk drives storing data sent from the host computer; a plurality of logical volumes relating to at least one of the disk drives; a first logical volume of the plurality of logical volumes, the first logical volume being recognized as an online logical volume by the host computer, and being a destination of a read/write command sent from the host computer; and a second logical volume of the plurality of logical volumes, the second logical volume being recognized as an offline logical volume by the host computer, wherein when the controller receives from the host computer a first read/write command to read/write a first data corresponding to the first read/write command from/to the first logical volume, the first read/write command including a first identifier of the first logical volume as a destination of the first read/write command and a first target information designating a first access address in the first logical volume as a first read/write target, the controller reads/writes the first data corresponding to the first read/write command from/to the first logical volume by referring to the first target information included in the first read/write command, and wherein when the controller receives from the host computer a second read/write command to read/write a second data corresponding to the second read/write command from/to the first logical volume, the second read/write command including the first identifier of the first logical volume as destination of the second read/write command and a second target information including a second identifier of the second logical volume and designating a second access address in the second logical volume as a second read/write target, the controller reads/writes the second data corresponding to the second read/write command from/to the second logical volume, instead of from/to the first logical volume, by referring the second target information included in the second read/write command.