ZFS + gmirror: how?

Robert Jesacher jessy at sicha.net
Mon Apr 28 12:22:18 UTC 2008

On 27/04/2008 20:44 Guus Houtzager wrote:
> Hi,
> I'm rather new to FreeBSD and I'm having trouble with ZFS and gmirror.
> I've used this guide to install FreeBSD 7 on ZFS:
> http://www.ish.com.au/solutions/articles/freebsdzfs
> This goes flawless, however, the /bootdir is still just /dev/ad01sa (in
> my case), so if that disk breaks, I still can't boot from ad1. So I
> thought I could just make a gmirror containing /dev/ad0s1a and ad1s1a
> and use that for /bootdir. This however does not work.
> What I did is:
> - gmirror load
> - gmirror label -v -b round-robin gm0 /dev/ad1s1a
> - newfs /dev/mirror/gm0
> - mount /dev/mirror/gm0 /mnt/tmp
> - dump -L -0 -f- /bootdir | (cd /mnt/tmp && restore -r -v -f-)
> - edit /etc/fstab and /mnt/root/etc/fstab: change all references to
> ad0s1a by /dev/mirror/gm0
> - echo 'geom_mirror_load="YES"' >> /boot/loader.conf
> - echo 'geom_mirror_load="YES"' >> /mnt/tmp/boot/loader.conf
> - reboot
> However: I can see the bootprocess starting first ZFS followed by a
> message saying it's waiting for GEOM gmirror to start, which it does
> after a little while and then I get a prompt where I can manually tell
> the system where the root filesystem is. And if I tell it
> zfs:system/root it does not work (my zpool is named system).
> Anyone know what I'm doing wrong and what's the best way to do this?
> Thanks in advance!
> PS: please CC me in any reply, as I'm not subscribed to this list. Thanks!
> Regards,

I'm not sure if this is the cause, but it looks like
/boot/zfs/zpool.cache might not be up to date or missing.

Once I had the same issue. You should boot up somehow (you can even use
the 7.0 install CD). Make sure you have the directory /boot/zfs and do a
"zpool import". After this you should have a valid zpool.cache file
which you need to copy to your mirror device.

PLMK if this works for you as this is also my desired setup. I "only"
need to make the gmirror step tough ;-)


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