> Essentially the MS RDC protocol is just rsync run twice in a row, with the rsync metadata copied via rsync to compress it further. There's an important diffe

> Essentially the MS RDC protocol is just rsync run twice in a row, with the rsync metadata copied via rsync to compress it further. There's an important difference is that RDC uses a locality-sensive hash algorithm (MinHash, IIRC) to find files likely to have matching sections, whereas rsync only considers the version of the same file sitting on the far host. rsync encodes differences on each file in isolation, whereas RDC looks at the entire corpus of files on the volume. For example, if you do the Windows equivalent of cat local/b.txt >> local/a.txt, rsync is going to miss the opportunity to encode local/a.txt -> remote/a.txt using matching runs from a common local/b.txt and remote/b.txt. However, RDC has the opportunity to notice that the local/a.txt -> remote/a.txt diff is very similar to remote/b.txt and further delta-encode the diff as a diff against remote/b.txt.