A disk array includes a drive management unit, which is a program for identifying types of disk devices and managing different disk devices separately, and a drive management table for storing information to be utilized by the drive management unit. The disk array further includes a program for managing accumulated time of disk devices. The program includes a drive lifetime setting portion for setting lifetimes of drives, a drive start/stop portion for intentionally starting/stopping ATA disk devices, and an operation time measurement portion for measuring accumulated operation time. Since it is necessary to be conscious of difference in reliability and performance among disk devices when forming a RAID, a drive type notification unit, which is a program for notifying of the type of a disk device when forming the RAID, is provided.