A first storage system copies data of a virtual area of a first virtual volume to a virtual area of a second virtual volume of a second storage system, monitors accesses with respect to multiple virtual areas of the first virtual volume, updates access information related to the accesses of the multiple virtual areas, and, based on the access information, reallocates data inside an actual area of a first pool allocated to the virtual area of the first virtual volume. The first storage system sends the access information to the second storage system. The second storage system receives the access information, and, based on the access information, reallocates data inside the actual area allocated to a virtual area of the second virtual volume.