In accordance with one embodiment of the invention, a storage system is configured as at least one logical unit including at least one disk device; a controller for executing a read processing or a write processing of data having been stored or to be stored in the logical unit which is a destination of a read request or a write request, in response to the read request or write request transmitted from the computer, wherein the controller receives an instruction from the computer to turn on or off a disk device corresponding to the logical unit; and wherein, based on the instruction, the storage system turns on or off the disk device corresponding to the logical unit independently of disk devices corresponding to the other logical units.