Abstract: A microprocessor 18 in a control device 13 of a data storage device determines that the read request has a sequential access property, when a transfer size of data specified by a read request from a host computer 11 is the same as a preset pre-fetch determination size and sends the data for the read request to the host computer 11. The microprocessor 18 also reads data in succeeding areas continuous to the data designated by the read request from a storage device 12 into a cache memory 20. The data storage device enables to reduce a number of access from the control device 13 to the storage device 12, improving a response time as well as throughput of the data storage device.

Abstract: A microprocessor 18 in a control device 13 of a data storage device determines that the read request has a sequential access property, when a transfer size of data specified by a read request from a host computer 11 is the same as a preset pre-fetch determination size and sends the data for the read request to the host computer 11. The microprocessor 18 also reads data in succeeding areas continuous to the data designated by the read request from a storage device 12 into a cache memory 20. The data storage device enables to reduce a number of access from the control device 13 to the storage device 12, improving a response time as well as throughput of the data storage device.

Abstract: An array/slice definition unit constitutes an array composed of a group of slices. The array is constituted by defining a storage area in a disk drive as a single physical array area of the array. The physical array area is divided to a plurality of areas under a certain capacity, and the divided areas are defined as the slices. A logical disk definition unit constitutes a logical disk by combining arbitrary plural slices of the slices contained in the array. A slice moving unit exchanges an arbitrary first slice entered into the logical disk and a second slice not entered into any logical disk including the logical disk.

Abstract: If one of the HDDs of a disk array fails, a disk array controller regenerates the data stored in the failed HDD and stores the regenerated data in another HDD used in place of the failed HDD. To be more specific, the disk array controller checks each of the stripes of the disk areas of the disk array and determines whether each stripe is used by a file system. This determination is based on a disk resource management table. Then, the disk array controller regenerates data by use of RAID technology only for a stripe that has been determined as being used by the file system.

Abstract: When a data update request is sent from a host computer, a main controller determines one of a plurality of disk cache units, which is used, in accordance with a striping group to which a stripe corresponding to the requested update data belongs. The main controller loads the block data, required for generating updated parity data for the stripe in units of blocks, in a parity generator in the corresponding disk cache unit via a cache memory in the determined disk cache unit. The corresponding parity generator generates corresponding parity data.

Abstract: If one of the HDDs of a disk array fails, a disk array controller regenerates the data stored in the failed HDD and stores the regenerated data in another HDD used in place of the failed HDD. To be more specific, the disk array controller checks each of the stripes of the disk areas of the disk array and determines whether each stripe is used by a file system. This determination is based on a disk resource management table. Then, the disk array controller regenerates data by use of RAID technology only for a stripe that has been determined as being used by the file system.