A file system layout apportions an underlying physical volume into one or more virtual volumes (vvols) of a storage system. The underlying physical volume is an aggregate comprising one or more groups of disks, such as RAID groups, of the storage system. The aggregate has its own physical volume block...http://www.google.com.au/patents/US7409494?utm_source=gb-gplus-sharePatent US7409494 - Extension of write anywhere file system layout
