I don't want to be that guy, but zfs on freebsd was kind-of-experimental until around 2012;AFAIK in 2012 (Freebsd 9) root on zfs was a manual process, and not that easy to upgrade. Root on zfs is somewhat "recent"- it took years to get to the installer. My company at the time was basically a bsd shop (openbsd and freebsd), and the opensolaris(12?) version was still quite ahead. Still have my opensolaris tshirt of "first 5000" :)