I haven’t been drawing enough attention to it, but there’s been a bunch of HAMMER filesystem activity lately: First, Tomohiro Kusumi has been working on HAMMER – these posts are a small subset of his commits. Second, Matthew Dillon has been working full steam ahead on HAMMER2. The HAMMER2 design document has been updated (read this!), and he’s already accomplished master->slave disk syncing.
It’s not ready for production, of course, which you may already realize, so don’t install it unless you want to work on the code.