PURPOSE: To effectively use an idle disk space on a network by each computer device.

CONSTITUTION: With respect to the logical volume which manages physical disks 101c, 102c, 102d, etc., provided in computer devices 101 to 103 connected through a network bus 100 as logical disks, the object of a physical volume in the logical volume is extended from physical disks in the same computer system to, for example, physical disks of another system through the network bus 100.