Patent ID: 7546433

Claim:
A storage system comprising: a host system that issues a data read/write request; an external storage apparatus that provides an external logical volume for storing the data; and a first storage apparatus that creates a first virtual logical volume, wherein, the host system makes a request to the first storage apparatus to map volume information composed of management information for the external logical volume; in response to the mapping request, the first storage apparatus maps the volume information for the external logical volume onto the first virtual logical volume and sends the volume information for the external logical volume and first virtual logical volume to the host system; based on the volume information for the external logical volume sent from the first storage apparatus, the host system searches for any virtual logical volume having the same volume information as the volume information for the first virtual logical volume or external logical volume, and sets the virtual logical volume searched for in this search as an alternate volume for receiving requests to read/write data from/to the external logical volume.