Patent ID: 7177991

Claim:
A storage system installation method for installing a second storage system into a computer system which includes a host computer and a first storage system which is coupled to the host computer, wherein the first storage system includes a first physical disk device, and the second storage system includes a second physical disk device and a disk controller coupled to the second physical disk device, said storage system installation method comprising the steps of: coupling the second storage system to the host computer; coupling the second storage system to the first storage system such that the second storage system can access the first storage system; correlating a first logical device configured in at least the first physical disk device of the first storage system with a second logical device in the second storage system, the second logical device being provided to the host computer for transferring data from the host computer to the first logical device, wherein said second logical device is not assigned to any exclusive storage area of the second physical disk device of the second storage system; defining a path between the second logical device and the host computer; changing an access target of the host computer from the first logical device of the first storage system to the second logical device of the second storage system; receiving a write request from the host computer to write data to the second logical device, wherein upon receiving the write request, the data is transferred by the disk controller of the second storage system to the first logical device of the first storage system; and writing, at the first storage system, the data received from the second storage system into the first physical disk device of the first storage system related to the first logical device.