Imagine an rsync that was A LOT smarter for backup use cases. Detecting files that have been renamed, files that have been compressed, similar files, files that have only been appended to, files that are the same across multiple systems (Oh, yeah, I probably already have a copy of this kernel file from this other host). Basically, deduplication as part of rsync.

Exactly what I'm looking for recently.. I dismissed ZFS (not mature on Linux) and btrfs (seems to be too complex and buggy as seen in a few horror stories)

So far I started using --link-dest for rsync, as explained in https://lincolnloop.com/insights/detecting-file-moves-rename... and used in https://github.com/dparoli/hrsync/blob/master/hrsync#L52

BorgBackup has most of what you're looking for, though it doesn't implement CDC and doesn't replicate the files as-is in the backup location (instead using a compressed/deduped/chunked storage format)

For single system backups I've switched to using restic and it's been pretty great. I don't trust Borg, a couple years ago I tried doing a recovery using it and ran into some unicode issue in, I believe, a filename, and I couldn't track down exactly what file it was or get any files backed up after that file in the archive. I ended up using another backup I had.

For my multiple backups to a backup host where I'm using rsync, restic really doesn't work (having 100+ systems backed up to the same destination).