Copying mirrored partitions - will this work?
jmc-freebsd2 at milibyte.co.uk
Sun Mar 21 10:09:22 UTC 2010
On Sunday 21 March 2010, Modulok wrote:
> On 3/20/10, Mike Clarke <jmc-freebsd2 at milibyte.co.uk> wrote:
> > 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.
> How valuable is your data?
In financial terms not very, but still valuable enough to not want to
> I recommend you make an offline backup.
Yes, I take regular backups but regard them as the "emergency parachute"
and prefer to not put myself in a position where I'm doing something
risky and the backup files are the only protection, so I'll be making
additional backups anyway.
> There's a lot of steps in
> your procedure which introduce room for error.
Yes, it's a bit of unknown territory for me but with 6 partitions on the
slice it does require fewer potentially dangerous manual steps (like
newfs or restore to the wrong device) so looks like an interesting
> 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.
That's a possibility to consider but would result in additional changes
to the mirror configuration, something I'd prefer to keep to a minimum.
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