A data storage system includes a storage device divided into a plurality of blocks for storing data for a plurality of volumes, and a processor to execute instructions for maintaining a block map corresponding to the data stored on the storage device. The storage system may be part of a storage system...http://www.google.com.au/patents/US7991973?utm_source=gb-gplus-sharePatent US7991973 - Data storage systems, methods and networks having a snapshot efficient block map
