A method for synchronizing a secondary volume with a primary volume in a
continuous data protection system begins by scanning a region of the
primary volume, which is then compared with a corresponding region of the
secondary volume. An identification of the scanned region is stored in a
compare delta map when the comparison results in a discrepancy between
the scanned region and the corresponding region. Data is copied from the
primary volume to the secondary volume, using the compare delta map as a
guide to locate the data to copy. If the data protection system has
failed just prior to the restore process being initiated, it is termed a
re-baseline, and the entire primary volume is scanned. If the data
protection system is active prior to the restore process being initiated,
it is termed a re-synchronization, and is optimized by scanning only
select regions of the primary volume.