Patent ID: 7392364

Claim:
A storage system accessed from a computer, coupled to the computer and a second storage system, comprising: a first target device functioning as a first object of access from the computer; a command device which is a second target device functioning as a second object of access from the computer; a logical device allocated to the first target device; and a storage system controller which includes a memory storing a plurality of programs for an external storage connection mechanism and a juke box system, each of which is executed by the storage system controller, wherein the storage system controller controls allocation of the logical device to a third target device in the second storage system by executing the plurality of programs for the external storage connection mechanism, so that the first target device in the storage system is allocated to the third target device in the second storage system through the logical device and the computer stores data into the third target device via the first target device and the logical device, wherein the storage system controller changes a first relation between the third target device in the second storage system and the logical device in the storage system to a second relation between a fourth target device in the second storage system and the logical device in the storage system by executing the plurality of programs for the juke box system in accordance with receiving a command from the computer to the command device at the command device, the command includes information identifying the fourth target device, wherein, after changing the first relation to the second relation, the storage system controller controls allocation of the logical device to the fourth target device in the second storage system based on a result of the changing by the execution of the plurality of programs for external storage connection mechanism, so that the first target device in the storage system is allocated to the fourth target device in the second storage system through the logical device in the storage system instead of being allocated to the third target device and the computer stores data into the fourth target device via the first target device and the logical device, and wherein the third target device in the second storage system stores a first data sent by the computer during a first period, the fourth target device in the second storage system stores a second data sent by the computer during a second period after changing the first relation to the second relation.