Zchunk: Another Format For Delta-Friendly Files With Good Compression Promises

Zchunk is a new file format aiming to be highly "delta-able" while maintaining a good compression ratio.

Work on Zchunk is being done by Jon Dieter, a contributor to Fedora. The Zchunk format is based upon Zsync and Casync while attempting to address some of their design shortcomings. Zchunk makes use of Zstd internally for its compression handling.

In terms of the performance benefits of Zchunk according to its author, "a zchunk file with an average chunk size of a few kilobytes and a 100KB dictionary ends up roughly 23% larger than a zstd file using the same compression level, but almost 10% smaller than the equivalent gzip file. Obviously, results will vary, based on chunk size, but zchunk generally beats gzip in size while providing efficient deltas via both rsync and standard http."

If you are interested in learning more about Zchunk, Jonathan Dieter announced it on his blog yesterday for the formal introduction while the BSD-licensed code for it is hosted on GitHub.