Various embodiments of systems and methods are disclosed for initially
synchronizing redundant data (e.g., a mirror, a replica, or a set of
parity information) with an original volume. State information identifies
which regions of the original volume are currently valid, and only valid
regions of the original volume are used to generate the values of the
redundant data during the initial synchronization. For example, if the
redundant data is a set of parity information, synchronizing the
redundant data involves calculating one or more parity values based on
the valid regions of the volume. If the redundant data is a duplicate
copy (e.g., a mirror or replica) of the volume, synchronizing the
redundant data involves copying the valid regions of the volume to the
duplicate copy of the volume. If the original volume includes any invalid
regions, unnecessary copying and/or processing for those regions can be
avoided during the initial synchronization.