When configuring volume allocation on a storage device, it is confirmed that design information on the volume allocation is in compliance with an operational policy of a system and there is no mistake in design so as to configure the volume allocation on the storage device in the case where there is no problem. A computer system including: a host computer 2; a storage device 3 for providing a volume to the host computer 2 via a one network 5; and a management computer 1 connected to the storage device 3 via a network 6, wherein when a storage manager configures volume allocation of the storage device 3, the management computer 1 gathers configuration information on the volume allocation from the storage device 3 and makes a comparison between design information on the volume allocation to be configured on the storage device 3 inputted by the storage manager and the gathered configuration information on the volume allocation so as to identify changes.