Abstract: A disk control unit for writing and reading data to/from at least one disk device on the basis of an input/output request of an upper apparatus includes a volatile cache memory for holding data of the disk device, a non-volatile cache memory and a recording format information table stored in the non-volatile cache memory for holding recording format information of the tracks of the disk device. A write cache control unit refers to the recording format information table so as to enable the upper apparatus to perform a writing process on the volatile cache memory even when corresponding data of the disk device do not exist on the volatile cache memory.

Abstract: A disk controlling apparatus creates sense data indicating the contents of an error and writes it into an intermediate buffer provided within the disk controlling apparatus together with the record normally read when a key portion or a data portion constituting a record is not normally read. The disk controlling apparatus searches the intermediate buffer for desired record, reads and informs an error while taking the sense data into consideration for each record. The disk controlling apparatus stores a write address in a memory at the time of writing data, and when data are normally written the write address is eliminated from the memory, while holding the address when data are not normally written. At the time of reading data, if the address which agrees with the read address is stored in the memory, the disk controlling apparatus reports an error to a host apparatus.

Abstract: A cache memory holds data of a disk unit on a track unit basis. Recording format information of the track in each disk unit is held in an LTD. For a write request from an upper apparatus, in case of a hit of the cache memory, a write cache control unit finishes a writing process on the cache memory and reports an end of process to the upper apparatus. In case of a mishit of the cache memory, a recording format is analyzed with reference to the LTD and a record position on the track to be developed in the cache memory is recognized, the writing process is finished on the cache memory and an end of process is reported to the upper apparatus.

Abstract: A disk controlling apparatus creates sense data indicating the contents of an error and writes it into an intermediate buffer provided within the disk controlling apparatus together with the record normally read when a key portion or a data portion constituting a record is not normally read. The disk controlling apparatus searches the intermediate buffer for desired record, reads and informs an error while taking the sense data into consideration for each record. The disk controlling apparatus stores a write address in a memory at the time of writing data, and when data are normally written the write address is eliminated from the memory, while holding the address when data are not normally written. At the time of reading data, if the address which agrees with the read address is stored in the memory, the disk controlling apparatus reports an error to a host apparatus.