Patent ID: 8095510

Claim:
A method for restoring data, the method comprising: restoring first data on a source volume from second data on a target volume, wherein the second data is a snapshot of the first data taken at time T 1 , such that each track on the target volume corresponds to a track on the source volume, wherein a track on the target volume includes a local copy of data that existed on a corresponding track on the source volume prior to T 1 , if data stored on the corresponding track on the source volume was modified since T 1 , wherein the second data does not contain a comprehensive copy of all of the first data on the source volume, wherein during the restoring: a read operation from a track on the source volume results in a read operation from the corresponding track on the target volume, if said read operation from the source volume was originated from a host system, and if the track on the source volume was not written to after the restoring started; and a read operation from a track on the source volume results in a local read from said track on the source volume, if said read operation from the source volume is a result of a read operation from a track on the target volume corresponding to the track in the source volume.