An example of an information storage system includes physical storage drives for providing real storage areas to a pool which is tiered into tiers different in performance, and a controller. The controller monitors accesses in a first tier in the pool. The controller determines a loaded state of the first tier based on the accesses to the first tier. The controller holds management information relating loads to the first tier to relocation speeds and/or modes of moving data in data relocation between a second tier in the pool and the first tier. The controller determines at least one of a relocation speed and a mode of moving data in data relocation between the second tier and the first tier based on the determined loaded state of the first tier and the management information.