Computer system, storage volume management method, and computer-readable storage medium

A computer system comprising:

• a storage apparatus;
• a host computer which accesses volumes provided by the storage apparat us;
• and
• a management computer, wherein:
• the host computer executes a control program and a guest OS running on the control program;
• the guest OS accesses one or more volumes allocated from the storage apparatus;
• the storage apparatus performs copy operations of the one or more volumes allocated to the guest OS;
• one of the host computer and the management computer executes a copy control program for controlling copy operations by the storage apparatus;
• the one of the host computer and the management computer, in accordance with the copy control program, obtains first information indicating at least a part of one or more volumes allocated to the guest OS at a given time from the control program;
• and
• the one of the computers, in accordance with the copy control program, compares the first information with second information indicating at least a part of one or more volumes having been allocated to the guest OS prior to the given time to check for a change in volume allocation to the guest OS and performs volume copy control for the guest OS in accordance with a result of the checking.