Some genius HN person reading this please port ZFS!
Of course, you don't need loadable kernel module support to extend the OpenBSD kernel.
But anyway, even one file is enough. The aggregate would no longer be clean BSDL.
It seems like a passion project from Matthew Dillon who seem to be crazy smart. I mean he fork and created his own BSD and then decided let's do HAMMER2 while we're at it.
Apparently it's one of the fastest for things like postgresql. Here are some benchmarks: https://www.phoronix.com/scan.php?page=news_item&px=HAMMER2-...