The performance to transfer data to external storage media in thin provisioning is enhanced.A storage apparatus is connected via a network to a host system writing of data and to a tape management apparatus for managing tape storage media for storing the data. The storage apparatus is designed so that data, for which a write request is issued by the host system, is stored in a virtual volume; a predetermined area in a plurality of storage devices is allocated to a data storage area in the virtual volume storing the data; and if the virtual volume is a backup object to be backed up to the tape storage media, a predetermined area in a specified storage device, from among the plurality of storage devices, is allocated to the data storage area in the virtual volume; and if the virtual volume is not a backup object to be backed up to the tape storage media, a predetermined area in an unspecified storage device, from among the plurality of storage devices, is allocated to the data storage area in the virtual volume.