Provided is a computer system including a plurality of storage apparatuses, in which, if the storage apparatuses employ an external mapping/connection system, the plurality of storage apparatuses can efficiently use each other's storage resources. The computer system includes a plurality of storage apparatuses and a management computer for managing the storage apparatuses. The management computer determines whether or not it is possible to perform external connection between the plurality of storage apparatuses and whether or not it is possible to divert the use of a storage device in one storage apparatus to another storage apparatus, on the basis of a criteria table, and if it is possible to perform external connection between the plurality of storage apparatuses, it is carried out and, if it is not possible, the management computer diverts the use of a storage device in one storage apparatus to another storage apparatus.