The present invention controls supply of power to a storage device on the basis of an access status, moves a logical storage device between physical storage devices having different power supply modes, reduces energization time, and improves the reliability. A relocation plan creation portion creates a relocation plan by disposing a logical volume with high access frequency in a RAID group which is in a long-time energization mode, disposing a logical volume with moderate access frequency in a RAID group which is in a first short-time energization mode, and disposing a logical volume with low access frequency in a RAID group which is in a second short-time energization mode. An execution time determination portion determines an execution time for executing the relocation plan, on the basis of the access frequency to the RAID groups. The volumes with higher access frequency are disposed in the RAID group in which the power supply time is long, and the volumes with lower access frequency are disposed in the RAID group in which the power is supplied in an on-demand fashion.