Patent ID: 7360037

Claim:
A storage controller connected to a host system, comprising: a first storage device; and a first control unit configured to control the first storage device, wherein the first control unit forms at least one first logical volume connected to the host system to provide a host logical volume and a plurality of second logical volumes to store data sent from the host system, the at least one first logical volume having a switchable association with the plurality of second logical volumes, wherein the first control unit is connected to an external storage controller having a second storage device and a second control unit configured to control the second storage device and forming a third logical volume associated with one of the second logical volumes, and wherein, when the first control unit switches from a first association with said one of the plurality of second logical volumes associated with the third logical volume in the external storage controller to a second association with another one of the plurality of second logical volumes which is not associated with the third logical volume, the first control unit controls power supplied to a driving mechanism of the second storage device.