Redundant disk array (raid) system utilizing separate cache memories for

Abstract

A memory device with a redundant disk array. In order to quicken the processing of data writing into the redundant disk array, a first cache memory for accessing the redundant disk array, a second cache memory for storing old data of the first cache memory when the data of the first cache memory are renewed, and a third cache memory for storing old CK data read out of the redundant disk array when the data of the first cache memory are renewed are provided. New CK data are produced from new data for the renewal, old data stored in the second cache memory and old CK data stored in the third cache memory, and the new data for the renewal and the new CK data are stored into data storage means and CK data storage means of the redundant disk array. Since, the data read out of the cache memories are processed without reading the old data and the old CK data out of the redundant disk array, the number of accesses into the disk array at a data writing time can be reduced, and data writing can be performed at a quick speed.