The data storage subsystem is implemented using redundancy groups of data storage modules, at least one module of which comprises a plurality of data storage elements. In this manner, the one dimensional data storage module redundancy group is expanded in another dimension by the use of a plurality of...http://www.google.com.hk/patents/US5566316?utm_source=gb-gplus-share專利 US5566316 - Method and apparatus for hierarchical management of data storage elements in an array storage device
