A storage system for covering advantages of the "In band method" and the "Out of band method", including an external storage device having storage data and storage operating data for operating the storage host computer connected to the external storage device on which an application is able to operate, and a storage operating server connected to the external storage device and the host computer, and having a storage operating server program, for obtaining the storage operating data from the external storage device, where the application operates the storage operating data through the storage data server program.