| 摘要 |
PROBLEM TO BE SOLVED: To reduce write seek time for each band in random writing.SOLUTION: A system controller 13 monitors a count value of a dirty counter 13A whenever data is cached in a NAND memory 16. If one of bands B1 to BM for which the count value of the dirty counter 13A exceeds a reference value is present, one of the bands B1 to BM is selected as a write band. If an amount of data corresponding to the write band and cached in the NAND memory 16 is smaller than a capacity of the write band to which the data is to be written, data written to a region of the write band that is not designated by a write command is retreated to a region, in which the number of times of rewrite is equal to or greater than a predetermined value, in the NAND memory 16. The data cached in the NAND memory 16 and the retreated data are read from the NAND memory 16 and written to the write band of a magnetic disk 2, 3. |
