There is provided a computer system comprising: a storage system for storing data; and a management server coupled to the storage system. The storage system comprises a first interface, a first processor and a first memory. The management server comprises a second interface, a second processor and a second memory. In the case of which a first storage system stops receiving a process request, the management server selects a second storage system which receives a process request directed to the first storage system in place of the first storage system to be stopped. The second storage system instructs the first storage system to change an identifier of the first storage system, and receives a process request directed to the first storage system by assigning the identifier of the first storage system before the change to the second storage system.