A hybrid LUN copy operation that ultimately produces a full LUN copy, but involves
a transient snapshot-copy-like intermediate stage. In one embodiment, a statically
pre-allocated copy LUN is initialized with references pointing back to the primary
LUN. Over time, the sectors, blocks, or other data-storage units of the primary
LUN are copied to the copy LUN, so that, in the end, a full copy LUN in completed.
In a second, alternative embodiment, both the primary LUN and copy LUN are READ
and WRITE accessible immediately following the nearly instantaneous initialization
of the copy LUN. In both embodiments, the copy LUN may be statically allocated.
The immediate-full-LUN-copy operations provided by the present invention further
enable rotatable copy-LUN groups, each copy LUN within a copy-LUN group representing
a full, robust copy LUN.
