One or a plurality of physical storage devices that provide a physical storage area are connected to first and second computers. The computer updates metadata indicating the address correspondence relationship between the logical address of the volume and the physical address of the physical storage area in the write processing performed based on a write request designating the volume. The first computer copies the metadata to the second computer while receiving the write request. When the address correspondence relationship indicated by the copied metadata portion is changed during copying of the metadata, the first computer updates the metadata portion and copies the metadata portion to the second computer.