To reduce the number of data copies between volume pools by preventing occurrence of unevenness of resource usage between the pools, provided is a computer system including: storage apparatus; and host computer coupled to the storage apparatus, the storage apparatus including physical storage device, the storage apparatus holding information associating virtual volumes and pools each including real storage areas of the physical storage device, the storage apparatus allocating, to the virtual volume of a write destination designated by the host computer, the real storage areas included in each of the plurality of pools corresponding to the virtual volume of the write destination, and storing the data therein, the computer system being configured to: determine, based on the information held by the storage apparatus, orders of priority of the volumes of the write destination by the host computers; and hold the determined orders of priority.