HAMMER's ability to snapshot an arbitrary directory is still something I deeply deeply deeply respect & wish btrfs or zfs had.
I'm not sure the status but HAMMERFS also supposedly was going to have solid transparent encryption, which is something I wish btrfs did. I'd really like to be able to take a fs snapshot, send it to a friend, have them load the snapshot volume, but be unable to access it. But as soon as I did show up at their place with my keys, we could instantly unlock it & use it. I understand ZFS does a better job of this all, but balancing ZFS pools & adding drives has always sounded impossibly hard compared to btrfs's "it just works" adding-drives to RAID scenarios.
Ahh, that does sound like a nifty feature! I didn't mean to so strongly imply HAMMER was a knock-off ZFS, more that it fills a similar niche, similar enough that ZFS's dominance kind of takes away from the "wow factor" of HAMMER.
It makes more sense (to me anyway) when you consider that at the time HAMMER was first released, the Linux port of ZFS had only just begun, and FreeBSD had just released their first port of ZFS. Btrfs was also still an out-of-tree patch then, only mainlined in 2009. (not to mention ZFS as a whole probably seemed much more shaky around 2010 with Sun's death-by-Oracle and OpenSolaris getting butchered)
I think back then, having a clean and functional "recreation" of ZFS with all the design bloat removed seemed really promising. Now, it's just a nice FS competing with other nice FSes, except with the downside of being on an "exotic OS". Shame :(
I'm not sure the status but HAMMERFS also supposedly was going to have solid transparent encryption, which is something I wish btrfs did. I'd really like to be able to take a fs snapshot, send it to a friend, have them load the snapshot volume, but be unable to access it. But as soon as I did show up at their place with my keys, we could instantly unlock it & use it. I understand ZFS does a better job of this all, but balancing ZFS pools & adding drives has always sounded impossibly hard compared to btrfs's "it just works" adding-drives to RAID scenarios.