1. A storage system comprising multiple storage subsystems receiving access from a host computer, and a management computer managing the multiple storage subsystems; wherein each of the multiple storage subsystems has one or more resources; the storage system is configured to define a virtual storage subsystem including at least a portion of the resource of a first storage subsystem within the multiple storage subsystems and at least a portion of the resource of a second storage subsystem within the multiple storage subsystems, and receive a management operation request designating the virtual storage subsystem or a resource belonging to the virtual storage subsystem; upon receiving the management operation request designating multiple resources belonging to the virtual storage subsystem and a resource operation content, if the multiple resources are included in the same storage subsystem, the management computer transmits the management operation request to the said same storage subsystem; and if the multiple resources are included in different storage subsystems, the management computer determines whether the designated operation content can be executed or not, and if the designated resource operation content cannot be executed, notifies an operator that the designated resource operation content cannot be executed.