Hitachi, Ltd.

Kosaku Kamabayashi

Takao Satoh

Katsunori Nakamura

Teruo Nagasawa

A disk cache control unit disposed between an upper-rank processor and a disk unit, comprising a cache memory for holding a copy of data stored in the disk unit, at least one first interface controller which checks, in response to an input/output command requesting data to be read from the upper-rank processor, whether or not the data requested by the command is stored in the cache memory, and requests a head positioning of the disk unit when the data is not stored in the cache memory, and a second interface controller which indicates head positioning to the disk unit in response to a head positioning request, notifies the completion of the head positioning to the first interface controller in response to a notice of the completion of the head positioning, and which reads data from the disk unit and stores the data in the cache memory when a data transfer request did not come in a specified time period set to read data from the disk unit without a rotational delay after a notice of the head positioning head been given to the first interface controller and the subsequent transfer of data from the second interface controller had been completed, and which gives a notice of storage of the data in the cache memory through memory means to the first interface controller, and in response to this storage notice, the first interface controller reads the data from the cache memory and transfers the data to the upper-rank processor.

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Odawara, Japan

Kosaku Kamabayashi