Liuba Shrira Hao Xu Thresher: An Efficient Storage Manager for Copy-on-write Snapshots. 57-70 2006 conf/usenix/2006g USENIX Annual Technical Conference, General Track http://www.usenix.org/events/usenix06/tech/shrira.html db/conf/usenix/usenix2006g.html#ShriraX06