In a storage system, a plurality of logical disks are constituted by
combining a plurality of physical disks. A logical disk management unit
converts input/output (I/O) requests addressed to the logical disks into
I/O requests addressed to corresponding physical disks, and outputs the
converted I/O requests. A physical disk management unit accesses the
corresponding physical disks in accordance with the I/O requests which are
output from the logical disk management unit and addressed to the physical
disks. A logical disk relocation control unit relocates the logical disks
so as to set the busy rates of the physical disks within a range between
the first state in which the ratio of the busy rates of the physical disks
is equal to the ratio of the I/O processing performance values of the
physical disks, and the second state in which the busy rates of the
physical disks are leveled. A data relocation method is also disclosed.
