A management computer manages the pool application information that indicates a pool application for a pool and the application condition information that indicates the condition for the pool application. The management computer calculates an excess storage capacity based on a pool usage status for the pool. The management computer specifies a pool application for the pool and the condition for the pool application based on the pool application information and the application condition information. The management computer judges whether the specified condition is satisfied even in the case in which a storage area having a storage capacity equivalent to or less than the calculated excess storage capacity is deleted from the pool. In the case in which the result of the judgment is positive, the management computer defines a capacity equivalent to or less than the excess storage capacity as an unused capacity.