Patent ID: 8745005

Claim:
Apparatus for facilitating recovery of a secondary volume having data indicative of changes made to data on a primary volume comprising: monitoring circuitry that identifies a synchronization point where a secondary volume B-tree is known to be consistent; circuitry that writes, in response only to an impending B-tree split, all B-tree nodes involved in the impending split into an intent log before the split is performed, the intent log thereby being indicative of inconsistency in the secondary volume B-tree since a most recently identified synchronization point; and circuitry which, in response to a failure or reboot occurring when movement of data between B-tree leaf nodes or update of a B-tree parent node is incomplete, uses the intent log to complete the split by finding the synchronization point, instantiating the B-tree, replaying the intent log, and inserting snapped blocks into appropriate leaves of the instantiated B-tree.