Patent ID: 8255646

Claim:
A storage apparatus, the storage apparatus comprising: a plurality of hard disk drives, wherein the hard disk drives are organized into a plurality of disk groups, wherein each of the disk groups includes one or more of the hard disk drives, wherein the hard disk drives provide a plurality of logical volumes to a host system, wherein each of the logical volumes is defined on one of the disk groups, and wherein each of the logical volumes has an expiration date, wherein the expiration date of each logical volume is a deadline for migrating the logical volume from a current disk group in which the logical volume is defined to another disk group; a first logical volume migration unit for migrating a first logical volume from a first disk group of the disk groups to a second disk group of the disk groups based on an external command, wherein some of the disk groups are targeted for power source shutdown and others of the disk groups are not targeted for power source shutdown, wherein the first disk group is among the disk groups that are targeted for power source shutdown and the second disk group is among the disks groups that are not targeted for power source shutdown, wherein the first logical volume migration unit migrating the first logical volume includes the first logical volume migration unit selecting the second disk group as a migration destination for the first logical volume based on an expiration date of the first logical volume and expiration dates of other logical volumes defined on the second disk group, and wherein the first logical volume migration unit migrates the first logical volume from the first disk group to the second disk group such that logical volumes that have a same expiration date are balanced among the disk groups that are not targeted for power source shutdown; a power source shutdown unit for shutting down a power source of a hard disk drive of the first disk group after the first logical volume is migrated by the first logical volume migration unit; and a second logical volume migration unit for migrating the first logical volume from the second disk group to a third disk group of the disk groups when the expiration date of the first logical volume is reached.