Hitachi, Ltd.

Tetsuzo Kobashi

Masahiko Sato

Atsushi Ishikawa

Akira Kojima

Tsuneo Hirose

Toshiyuki Haruna

Nobuyuki Saze

Akira Yamamoto

Takao Satoh

Tetsuhiko Fujii

Norikazu Takayama

Kousuke Fujii

Nobuyoshi Ushijima

Yoshihiko Yano

Jun Isozaki

Yoshinobu Kudoh

In a system including a plurality of rotatable media type memory devices and disk array storage including in a redundant configuration a plurality of controllers each including a disk array control unit in which a plurality of SCSI bus coupling ports are individually coupled with respective ports of a plurality of host PCs/WSs via SCSI cables, the disk array control unit includes a function to logically transmit a bus operation such as a device or bus reset operation in an arbitrary one of the ports of the disk array storage to other ports. This makes it possible that the ports seems to be physically coupled in a daisy chain when viewed from the host PCs/WSs.

Bus controlling system

A rotary storage device includes a plurality of disk units, an upper-level interface circuit, a cache controller, a cache memory, and a control processor. In each disk unit, the storage area of each disk is subdivided into an ordinary user data area and a secondary cache data storage area including a group of consecutive cylinders. Data overflowed from the cache memory is sequentially written in the secondary cache data storage area so as to be later transferred therefrom to areas of the user data area according to addresses inherent thereto when traffic of upper-level input/output processing is relatively low. In the case of when data is sought to be accessed in the cache memory during a data read operation, access operations are performed first to the secondary cache data storage area and then to the user data area.

Rotary memory storage device with cache control method and apparatus

A cache control method and a rotary storage device are capable at a low cost, of improving the hit rate and minimizing the processing time in the event of a miss hit. The rotary storage devices includes a plurality of disk units, an upper-level interface circuit, a cache controller, a cache memory, and a control processor. In each disk unit, the storage area of each disk is subdivided into an ordinary user data area and a secondary cache data storage area including a group of consecutive cylinders. Data which has overflowed from the cache memory is sequentially written in the secondary cache data storage area so as to be later transferred therefrom to areas of the user data area according to addresses inherent thereto when traffic of upper-level input/output processing is relatively low. In the case of a miss hit of the cache memory during a data read operation, access operations are performed first to the secondary cache data storage area and then to the user data area.

Cache control method and rotary storage device having cache control

A disk subsystem provided with a cache has a capability of executing writing of data of discontinuous dirty blocks on a cache memory into a disk and reading of data of discontinuous empty blocks on the cache memory through the effect of just one DMA transfer. When the dirty data discontinuously ranged on a cache segment is written on the disk, the microprocessor provides a bit-map to a harddisk controller (HDC) as control information for data transfer. If an i-th bit of the bit-map is '1', the HDC operates to write the i-th block data sent from a direct memory access controller (DMAC) onto the corresponding sector of the disk. If the i-th bit is '0', the microprocessor serves to stop the write of the data and control a read/write head to wait until it passes the corresponding sector.

Method and device for transferring noncontiguous blocks in one transfer

A method of forming servo information in a magnetic disk apparatus of a sector servo system. Servo information is recorded in advance at the beginning of each of the sectors, and includes a DC erase signal, a track address signal and a burst signal. The track address signal indicates on which track of the magnetic disk the sector is located, and is formed by expressing the track address in Gray code and interleaving a dummy code into the Gray code. Servo information is recorded using an NRZI system or an RLL coding method. Servo information in which the dummy code is interleaved is decoded after the dummy code is removed at the time of demodulation.

Magnetic disk apparatus

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Odawara, Japan

Tetsuzo Kobashi