A drive unit connected to a disk control unit of a disk array has a logical group formed of a plurality of drives. In the logical group, both original data and duplexed data of the original data are stored. The original data and the duplexed data thereof are stored in different drives. When a plurality...http://www.google.com/patents/US5636356?utm_source=gb-gplus-sharePatent US5636356 - Disk array with original data stored in one disk drive and duplexed data distributed and stored in different disk drives
