The management computer allocates a volume of an external storage device to a host so as to satisfy performance requirements specified from the host. The management computer selects a path that is formed including a first port of the storage device and a second port of the external storage device and that satisfies the performance requirements from the host, and then sets the priority. The management computer sets to the host the use authorization of a primary port and a secondary port that constitute a selected path and the use authorization of a second logical volume.