| 摘要 |
PROBLEM TO BE SOLVED: To eliminate unnecessary processing for layer control if data returns to an original layer.SOLUTION: A moving processing unit 42 holds data in a layer moving source area if a free capacity of a layer moving source is not less than 10%. A read processing unit 43 reads data from a low-load layer if the data for which a read request is received is present in a plurality of layers. A write processing unit 44 stores an update state in a bitmap table 31 without updating a copy if a load is high, and updates copy data in situations in which a low load state continues for ten or more minutes. |
