A RAID apparatus that at least duplicates identical data to store thus duplicated data, which, when an instruction of writing data is given, writes data to a local cache and to a mirror cache, and writes data of the local cache to a primary disk and writes data of the mirror cache to a secondary disk....http://www.google.de/patents/US7610446?utm_source=gb-gplus-sharePatent US7610446 - RAID apparatus, RAID control method, and RAID control program
