RAID management apparatus, RAID management method, and computer product

In a first management unit for a redundant array of independent disks (RAID management-unit), a shared-class setting unit receives a shared-class setting command, for example, from a host computer. If the shared-class setting command includes information about the first RAID management unit and a second RAID management unit, a shared management-information creating unit creates shared management information, writes the created shared management information onto a first disk, notifies the second RAID management unit corresponding to a second disk about the shared management information, and gives an instruction to write the shared management information onto the second disk. The second RAID management unit then writes the notified shared management information onto the second disk.