[blaz0]

I like zsync quite a bit. The chunking patcher we wrote for League of Legends is similar to zsync in some key ways.

One of the things we did to improve the efficiency of the core rolling hash based chunking logic was to add file type aware chunking. Basically, we teach the patcher about the different archive formats that our games use (say, Unreal Engine PAKs) and the algorithm ensures that chunks stop at the file boundaries within the archive, so a chunk doesn’t straddle two unrelated entries. That way when files move around in the archive we can more reliably match their chunks across versions. I think this helped improve download sizes by 5-10% in our case.