with all due respect here - I've never heard of it either, and that's not what you want with a filesystem.

The draw of ZFS is that it's the log-structured filesystem with 10 zillionty hours of production experience that says that it works. And that's why BTRFS is not a direct substitute either. Or Hammer2. There are lots of things that could be cool, the question is are you willing to run them in production.

There is a first-mover advantage in filesystems (that occupy a given design and provide a given set of capabilities). At some point a winner sucks most of the oxygen out of the atmosphere here. There is maybe space for a second place winner (btrfs), there isn't a spot for a fourth-place winner.