ZFS Volumes not showing up on reboot?

If you're using ZFS on FreeBSD and your ZFS volumes do not appear after rebooting the system, verify that your rc.conf file has zfs_enable="YES". This allows /etc/rc.d/zvol to run, which executes an undocumented 'zfs volinit' command to create the /dev/zvol/... device entries. The script also adds swap space volumes if the ZFS volume has org.freebsd:swap=on set.