I can't find a BTRFS based NAS OS

I happened to be browsing the forum of another well-known NAS OS solution, and came across a thread regarding improved btrfs support in their next release.
I noticed that part way through the thread the OP posted the comment ‘The problem is I cant find a btrfs based NAS OS’, which surprised me a little as a google search for ‘btrfs based nas os’ brings up Rockstor on the first results page.
Anyway, I discretely tapped him on the shoulder and pointed him in this direction.