bita VS kysync

Built this cdc tool for software update of embedded (Linux) systems and have deployed it with good enough performance on a couple of arm CPUs; https://github.com/oll3/bita

Though main goal has been keeping data usage low rather than speed up.

Nice write up. rsync is great as an application but I found it more cumbersome to use when wanting to integrate it into my own application. There's librsync but the documentation is threadbare and it requires an rsync server to run. I found bita/bitar (https://github.com/oll3/bita) which is inspired by rsync & family. It works more like zsync which leverages HTTP Range requests so it doesn't require anything running on the server to get chunks. Works like a treat using s3/b2 storage to serve files and get incremental differential updates on the client side!

Very cool, thanks for sharing. I did a deep dive in the past into various syncing/binary diff protocols and really liked zsync. It was probably my top choice for the application I was designing but I ended up not using it. The library I did use is called bita: https://github.com/oll3/bita. It is inspired by the same family of projects as zsync. The main advantage I found with bita is that the core logic is encapsulated in a library so that you don’t only have to use the binaries but can integrate it directly into an application. I’d be curious to know if that’s in the plans for KySync.

KySync is released under the MIT Open Source License (see COPYING in root of repository).

KySync is an efficient way to distribute new data which makes use of older (but similar) data that you may already have present locally. KySync supports HTTP v1.1, but can easily be extended to support any server protocol which supports range queries.

KySync is [released](https://github.com/kyotov/kysync/releases) under the MIT Open Source License (see [COPYING](https://github.com/kyotov/ksync/blob/master/COPYING) in root of repository).

KySync is a full rewrite of [Zsync](http://zsync.moria.org.uk/) in modern C++. While no code was reused from Zsync, the awesome [Zsync technical paper](http://zsync.moria.org.uk/paper200503/) was the major resource used for the implementation of KySync.

The value proposition of KySync over Zsync is that it takes advantage of modern architecture features (multi-core multi-CPU systems as well as exceedingly fast IO subsystems, e.g. NVMe SSDs). KySync is 3x-10x (or more) faster than Zsync on such commonly available modern hardware. We have not spent much time optimizing KySync single-thread performance, so there are cases where with sufficiently high similarity, Zsync is faster when less then 4 threads are used in KySync.