Patent ID: 7673110

Claim:
A computer system, comprising: a first computer; a second computer that is connected to the first computer; a first storage device system that is connected to the first computer and the second computer; a second storage device system that is connected to the first computer and the second computer; and a third storage device system that is connected to the first storage device system and the second storage device system, wherein the first storage device system has a first storage area, the second storage device system has a second storage area, and the third storage device system has a third storage area, wherein the third storage area stores data which the second computer uses, wherein the first storage device system has a first virtualization unit and the second storage device system has a second virtualization unit, wherein the first virtualization unit of the first storage device system provides the third storage area in the third storage device system to the second computer as the first storage area in the first storage device system, wherein the first computer instructs the second computer to recognize the second storage area, wherein the second virtualization unit of the second storage device system provides the first storage area in the first storage device system to the second computer as the second storage area in the second storage device system after providing, by the first virtualization unit of the first storage device system, the third storage area in the third storage device system to the second computer, wherein as an alternative to a first path in which an input/output request from the second computer to the third storage area through the first storage area is performed, the first computer instructs the second computer to set a second path in which an input/output request from the second computer to the third storage area is performed through the second storage area, wherein the first computer instructs the second computer to prohibit input/output requests to the third storage area, such that the input/output requests are prohibited through the first path, wherein the first computer instructs the second storage device system to change an access privilege so that the third storage area is accessible by the second storage device system, wherein the first computer instructs the second storage device system to set the second storage area corresponding to the third storage area, wherein the second storage device system sets the second storage area based on the instruction to set, and wherein the second virtualization unit of the second storage device system provides the third storage area to the second computer as the second storage area.