1. A storage system having a plurality of management servers and one or more storage apparatuses that change their own configurations in accordance with configuration change operations performed by the management servers, wherein each of the management servers comprises a server-side configuration change management unit for managing the history of configuration change operations it performs for the storage apparatuses; each of the storage apparatuses comprises a storage apparatus-side configuration change management unit for managing the history of configuration changes it makes in itself in accordance with the configuration change operations performed by the management servers; the server-side configuration change management unit transmits, when necessary, a request to undo a configuration change operation to the storage apparatus; when the storage apparatus-side configuration change management unit receives the request to undo the configuration change operation, it judges whether the undo target configuration change operation and its relevant configuration change operations performed after the target configuration change operation have involved a further relevant configuration change operation for another storage apparatus, and if they have not involved a further relevant configuration change operation for another storage apparatus, the storage apparatus-side configuration change management unit performs undo processing only for the configuration change made in accordance with the target configuration change operation, but if they have involved a further relevant configuration change operation for another storage apparatus, the storage apparatus-side configuration change management unit makes a request to the management server that performed the further relevant configuration change operation to undo it; and in response to the request for undo processing from the storage apparatus, the server-side configuration change management unit transmits an undo request requesting undo processing for the further relevant configuration change operation to the corresponding storage apparatus.