ReDD: Reverse Directory Deltas
ReDD is a "reverse delta" scheme that permits the reconstruction of an earlier version of a set of files starting from a given full set of files. In a chain of ReDD version deltas, access to prior version N-M starting from version N requires the sequential reconstruction of versions N-1, N-2, ..., N-M, so the later the version the faster the access. Because later versions don't depend on earlier versions, the old part of a chain broken at an arbitrary point can be discarded without adjustment to the remainder of the chain. Any ReDD version can also be represented with a full set of files rather than with deltas, which may be useful for caching recently reconstructed versions or for establishing points of departure for runs of deltas. Typically, full file sets occur in the latest version at the head of a chain and in any versions that serve as checkpoints or cover interior modifications of the original version chain.
Includes ReDD implementation.
- Ed Summers, Library of Congress: http://github.com/edsu/dflat