Ffs
From Hackepedia
You will want to check out soft-updates if you have ffs, and most likely install it on all partitions except /:
$ less -XF /usr/src/sys/contrib/softupdates/README
To see if you have soft-updates enabled:
$ mount /dev/ad0s1a on / (ufs, local) devfs on /dev (devfs, local) /dev/ad0s1g on /backup (ufs, local, soft-updates) /dev/ad0s1e on /tmp (ufs, local, soft-updates) /dev/ad0s1f on /usr (ufs, local, soft-updates) /dev/ad0s1d on /var (ufs, local, soft-updates)