Copying mirrored partitions - will this work?

Modulok modulok at
Sun Mar 21 01:48:57 UTC 2010

How valuable is your data?

I recommend you make an offline backup. There's a lot of steps in your
procedure which introduce room for error. You could perhaps disconnect
one of the hard drive's data cable (same thing). Also, make a backup
copy of your geom meta data somewhere.

Other than that, your procedure sounds like it should work. Though,
I've never tried it. I do recall, that when updating from 6.2-RELEASE
to 8-RELEASE, the geom meta data was automatically updated. I'm not
sure if there is any change between Release and Stable, though. I'm
also not sure if it was a backward incompatible change, as I never
went back to 6.2. Just something to be aware of.

Sorry I can't be more helpful. Maybe someone else knows more.

On 3/20/10, Mike Clarke <jmc-freebsd2 at> wrote:
> I'm currently running 8.0-RELEASE and am considering experimenting with
> 8.0-STABLE. I'd like to preserve my existing system in case things go
> pear-shaped so I'll copy the entire system onto a spare slice and then
> use csup to upgrade the copy to STABLE. Normally I'd go through the
> steps of bsdlabel, newfs and then dump|restore to create the copy but
> I'm wondering if I can take advantage of my recently created gmirror to
> cut down the work.
> I have two 500GB disks, /dev/ad4 and /dev/ad8, each partitioned into 4
> slices of 88, 88, 42 and 259GB. My system is installed on the first
> slices (ad4s1 and ad8s1) which are mirrored as /dev/mirror/gm0. The
> second slices (ad4s2 and ad8s2) are currently unused. My thoughts are
> to temporarily add ad4s2 into gm0 with "gmirror insert gm0 ad4s2" and
> wait for the mirror to synchronise. I should then be able to remove the
> temporary addition with "gmirror remove gm0 /dev/ad4s2" at which point
> ad4s2 should be a duplicate of the original system and I can then go
> ahead and create a new mirror with "gmirror label -b load gm1 ad4s2"
> and "gmirror insert gm1 ad8s2". After editing /etc/fstab in the new
> mirror to use gm1 instead of gm0 I should then be able to boot into the
> system on slice 2 and upgrade it to STABLE while still keeping my
> original system to fall back to if required.
> Is this approach of moving disks from one mirror to another workable, or
> have I missed something that would lead me into deep trouble? I don't
> mind unduly if I make a mess of the second slice and have to start
> again but I don't want to lose the contents of my original system on
> slice 1.
> --
> Mike Clarke
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