Disk array system having an extended load balancing function

摘要

A disk array system including plural magnetic disk drive groups each constructed by plural magnetic disk drives and a disk controller for controlling data transfer between the plural magnetic disk drive groups and an upper unit. The disk controller obtains a use frequency (I/O load) with respect to each magnetic disk drive group and selects a combination of the magnetic disk drive groups on the basis of the use frequency. Logic volumes from the upper unit and allocated in each magnetic disk drive group before the combination are reallocated among the combined magnetic disk drive groups, thereby concatenating the magnetic disk drive groups.