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.

Abstract: A method and system for mirror storage element resynchronization in a storage virtualization device is disclosed. According to one embodiment of the present invention, a read operation on a region of a data volume is received at a first module of a first storage virtualization device where the data volume is associated with at least a first mirror storage element and a second mirror storage element, a state indicated by a bit corresponding to the region of the data volume within a first synchronization map is determined in response to receiving the read operation, the read operation is processed using the first module if the bit is determined to indicate a first state and using a second module of the first storage virtualization device if the bit is determined to indicate a second state.

Abstract: A method, system, computer system and computer program product to maintain consistency between mirrored copies of data. A first data change map identifies regions that are about to be updated. If a system failure occurs during the update, the first data change map identifies regions that were being changed so that only those regions can be synchronized to restore consistency between the mirrored copies of data. A second data change map tracks changes made to data after a snapshot of the mirrored data is taken. This second data change map enables the mirrored copies of data to be synchronized without copying all data from one mirrored copy to another. The first and second data change maps are updated in parallel to reduce processing time and overhead. This parallel processing enables fast restoration and synchronization of mirrored copies of data, while having minimal effect on performance of applications using the data.