Patent ID: 7793148

Claim:
A method for synchronizing data between a primary site and a secondary site, comprising: copying updates from a primary first storage at the primary site to a secondary first storage at the secondary site during system operations; maintaining at least one second storage comprising a secondary storage at the secondary site; performing a failover from the primary site to the secondary site after a failure at the primary site; making a virtual copy of the secondary first storage to the secondary second storage in response to the failover; performing a failover from the secondary second storage to the primary first storage in response to making the virtual copy, wherein read and write operations are performed with respect to the secondary second storage after the failover, and wherein copying only updates made to the secondary site comprises copying the updates to the secondary second storage during the failover from the primary first storage; and in response to a recovery at the primary site, performing: copying data from the secondary first storage to overwrite data units at the primary first storage updated before the failover that were not copied to the secondary first storage; and using the at least one second storage after recovery to copy only updates made to the secondary site after the failover.