Patent ID: 8516204

Claim:
A storage system, comprising: a control device electronically coupled to a host computer and a plurality of disk drives configured as a plurality of redundant array of independent disks (RAID) groups, wherein the control device is configured to: control input and output of data between the host computer and the plurality of disk drives; set a first logical volume and a plurality of second logical volumes, the first logical volume being an access target of the host computer, each of the plurality of second logical volumes belonging to one of the plurality of RAID groups; set a mapping relation between the first logical volume and the plurality of second logical volumes, the first logical volume corresponding to one of the plurality of second logical volumes on the mapping relation; store the data issued from the host computer to the first logical volume in a certain second logical volume which is one of the plurality of second logical volumes and corresponds to the first logical volume based on the mapping relation; and set a third logical volume for storing control information to change access from said certain second logical to another second logical volume, wherein the third logical volume has different content from the first logical volume and the plurality of second logical volumes, wherein if the control device receives a write command to the third logical volume from the host computer, the control device is configured to identify the certain second logical volume and the another second logical volume in the third logical volume in response to the write command, and to switch the certain second logical volume, corresponding to the first logical volume on the mapping relation, to the another certain second logical volume of the plurality of second logical volumes, and in response to the switching the control device is configured to rotate a first plurality of disk drives configured as a first RAID group to which the other certain second logical volume belongs and stop motors of a second plurality of disk drives configured as a second RAID group to which the certain second logical volume belongs.