A technology for automatically judging which media of tier is optimum for storing data on and allocating the data to that tier. It accomplishes efficient media utilization without the user being aware of the storage location. For example, frequently accessed data is allocated to high-speed, high-performance media, while infrequently accessed data is allocated to low-cost, large-capacity media. As a result, it becomes possible to improve the access performance in regard to frequently accessed data and to lower implementation and operating costs of storage by effectively utilizing low-cost media.
