Abstract: A method, system, computer system and computer program product to synchronize data and a snapshot of the data taken at a given point in time. Persistent data change maps are used to track changes made to data after a snapshot of the data is taken. Changes to the data are tracked using a persistent accumulator map, and changes to the data with respect to a second set of data are tracked using a persistent volume map. The persistent accumulator map is updated with each update of the data. Persistent volume maps are updated when a subsequent snapshot of the data is taken. Only changes to the data made after the snapshot was taken are applied to synchronize the snapshot with the data so that all of the data is not copied. Snapshots can be located in a physically separate location from the data itself.