FreeBSD HOWTO: Software Mirror System Disk
dannyman at toldme.com
Mon Jan 24 12:15:16 PST 2005
[ From http://dannyman.toldme.com/2005/01/24/freebsd-howto-gmirror-system/ ]
A new feature of FreeBSD 5.3 is the ability to set up a software mirror
of your system disk. This allows you to boot off either of a pair of
hard disks, which will then function as a RAID1, which will ensure
system uptime in the face of a single disk failure.
As the documentation is a bit sketchy, here’s a quick cheat sheet for
setting this up with gmirror:
(This crib sheet assumes you have a pair of identical IDE (in my case,
SATA) drives identified as ad4 and ad6.)
1. Install FreeBSD on to ad4.
2. Reboot with the Install CD.
3. Enter Fixit mode, using Install CD disc2 as the “live filesystem”
4. # *chroot /dist*
# *mount_devfs devfs /dev*
# *gmirror label -v -b round-robin gm0 /dev/ad4*
# *gmirror insert gm0 /dev/ad6*
# *mount /dev/mirror/gm0s1a /mnt*
# *echo ‘geom_mirror_load="YES"‘ >> /mnt/boot/loader.conf*
# *echo ’swapoff="YES"‘ >> /mnt/etc/rc.conf*
5. Edit /mnt/etc/fstab to convert ad4 -> mirror/gm0
Thanks to the few dozen people who have come before me, and posted
crucial hints to the mailing lists. Thanks also to Ralf S. Engelschall
who has a far more verbose explanation of how to do this sort of thing
with mis-matched disks. [See http://people.freebsd.org/~rse/mirror/ ]
You should definately look over the gmirror man page, and review the
output of *"gmirror list gm0"* when swapping out drives. You can disable
automatic rebuild, etc. It is quite nice.
More information about the freebsd-questions