Some notes on RootOnZFS article in wiki

Scot Hetzel swhetzel at
Mon Dec 21 18:47:49 UTC 2009

On 12/21/09, Mel Flynn <mel.flynn+fbsd.current at> wrote:
> Hi,
>  yesterday went through the RootOnZFS (gpt mirror version) and here's a few
>  notes:
>  1) You cannot use the install CD. It doesn't have a livefs and so you can
>  never do the actual install in 2.2. The DVD will work and the USB image. I
>  ended up using the livefs CD and the USB image, cause I didn't want to loose
>  the work I already did.

I have updated the wiki to mention that you need an install media with
the livefs support.

>  2) `gpart set -a active -i 1 ad4' gave me 'active: device not configured'.
>  This error isn't mentioned (debugflags didn't help) in the wiki nor the
>  missing DIAGNOSTICS section in the gpart man page. In my case the system
>  booted, but it's nice to know what the error means and whether you can ignore
>  it.

I had marked that step as optional, and as was stated in this thread
it is not needed for GPT disks.   This optional step has been removed
from the wiki.

>  3) By adding the swap partitions on the two mirrored disks to /etc/fstab top
>  actually shows the sum of these as available swap. My expectation is/was that
>  the swap would be mirrored and thus I'd have only the size of one swap
>  partition. If this isn't the case, can I get by with 1 of the two since
>  they're double the intended size or should one use 2 and thus create them half
>  the intended size?

To mirror the swap partitions, your will need to use gmirror.

1. comment out/remove the /dev/gpt/swap{0,1} entries
2. add geom_mirror_load="YES" to /boot/loader.conf
2. reboot to make sure the system is not using the swap partitions
3. create the mirrored swap partitions using the gpt/swap0 and
gpt/swap1 partitions:

gmirror label -b prefer swap gpt/swap0 gpt/swap1

NOTE: round-robin can also be used, but see the gmirror(8) man page
about kernel dumps.

4. change /etc/fstab to use the mirrored swap partition:

/dev/mirror/swap                 none                    swap    sw
          0       0

If you try this, let me know how it turns out.


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