After more than one month (order placed on February 27, 2007) I still haven’t received the Premier Edition upgrade.
Please see my post on Google Apps discussions:
Never seen such bad and unprofessional support for a (future) paid service and I highly recommend against buying this service.
gmirror label -v -b round-robin gm0 /dev/ad0
echo geom_mirror_load="YES" >> /boot/loader.conf
sed -i .orig 's/ad0/mirror/gm0/' /etc/fstab
gmirror insert gm0 /dev/ad2
Replace ad0 with your FreeBSD bootdisk, ad2 with the second (same or larger capacity) disc.