Computer systems having a plurality of storage systems could not detect addition of storage systems or configuration changes thereof and automatically redistribute existing volumes based on “hints” provided when the volumes were created. A management computer, which is connected via a network to storage systems having volumes connected via a network to a host computer and which stores data used by the host computer, keeps correspondences between levels indicating specific performances of volumes and storage system characteristics indicating performances of the storage systems. From a first storage system, a level is obtained indicating a performance of a volume of the first storage system allocated to the host computer. The storage system characteristics of the first storage system corresponding to the obtained level indicating the performance of the volume, and storage system characteristics of another storage system are referenced, and the performances of the volumes of the storage systems are compared.