Restore a ZFS mirror setup (GPT, ZFS-on-root)

[Damien Fleuriot]

On 23 Oct 2011, at 11:26, James Coldwell <coldwelljames11 at googlemail.com> wrote:

> Hello List,
> 
> My Problem:
> My server wouldn't come back up after a reboot.
> It is a 8.2-RELEASE system, running a two-disk ZFS mirror setup.
> It is a dedicated box in a remote datacenter.
> I can boot up some linux-based rescue system.
> 
> The way I installed FreeBSD on it was with mfsbsd, the zpool was
> created as such:
>     set poolname="z0"
>     set dev1="ad4"
>     set dev2="ad6"
>     set swapsize="4G"
>     set zfssize="300G"
>     gpart delete -i 1 ${dev1}
>     gpart delete -i 1 ${dev2}
>     gpart destroy ${dev1}
>     gpart destroy ${dev2}
>     gpart create -s gpt ${dev1}
>     gpart create -s gpt ${dev2}
>     gpart add -b 34 -s 64k -t freebsd-boot ${dev1}
>     gpart add -s ${swapsize} -t freebsd-swap -l swap0 ${dev1}
>     gpart add -s ${zfssize} -t freebsd-zfs -l disk0 ${dev1}
>     gpart add -b 34 -s 64k -t freebsd-boot ${dev2}
>     gpart add -s ${swapsize} -t freebsd-swap -l swap1 ${dev2}
>     gpart add -s ${zfssize} -t freebsd-zfs -l disk1 ${dev2}
>     gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ${dev1}
>     gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ${dev2}
>     zpool create ${poolname} mirror /dev/gpt/disk0 /dev/gpt/disk1
> 
> That worked perfectly for half a year.
> Suddenly, it wouldn't come back up after a reboot.
> 
> What I want to do now is mount the filesystem and check for misconfiguration.
> So I once again booted into the linux-based rescue system, dd'd mfsbsd
> onto the first disk (/dev/sda), booted it up.
> This FreeBSD-based system is called "prealpha".
> That's where I am now:
>     prealpha# gpart show
>     =>        0  976773168  ada0  BSD  (466G)
>               0         16        - free -  (8.0K)
>              16      65520     1  !0  (32M)
>           65536  976707632        - free -  (466G)
> 
>     =>       34  976773101  ada1  GPT  (466G)
>              34        128     1  freebsd-boot  (64K)
>             162    8388608     2  freebsd-swap  (4.0G)
>         8388770  629145600     3  freebsd-zfs  (300G)
>       637534370  339238765        - free -  (162G)
>     prealpha# ls /dev/gpt/
>     disk1    swap1
> The devices changed name from ad4/ad6 to ada0/ada1 because mfsbsd
> loads the ahci module now.
> I want to mount the zpool from ada1, and view/edit some configuration files.
> After that, I want to restore the mirror setup with ada0 and ada1 and
> try to boot again.
> 
> How do I do that?
> Any help would be appreciated, I probably forgot to mention vital
> details, I am in a bit of a panic right now.
> Please tell me if you need for details.
> 

Did you try zpool import ?