I thought I'd add something about DragonFly on old hardware to this thread. On DragonFly, UFS is slow and outdated compared to FreeBSD, so a HAMMER or 2 is always the high-performance choice for everything except /boot. HAMMER2 isn't very RAM-hungry, and modern DragonFly with it on my oldest PC, a 2007-ish AMD Athlon box with 1GB of RAM, performed similarly in 2019 to how I remember 32-bit DragonFly performing on it in 2009. (The biggest difference, now to then? With 1GB of RAM, say bye-bye to use of modern web browsers.)