I'm using zrepl to sync ZFS filesystems incrementally between servers.

I like the ability to incrementally send only the changes of an encrypted filesystem to a target server that never had the encryption key at anytime.

I'm using this to share backup space with my friends. We both push/pull our encrypted snapshot diffs every hour. I don't have my friends' keys so I can't read their data, and they can't read mine. In case of emergency, I can go to their place with my key, and recover my data from their systems.