[linux-lvm] How to start duplicate VG with new name and UUID?

[linux-lvm] How to start duplicate VG with new name and UUID?

[Richard Michael]

Hello list,

I'm using FC7 2.6.23.12-52.fc7 and LVM2 lvm2-2.02.24-1.fc7.

I have a RAID1 mdadm software array containing a VG.  Half the array has
been removed from the system and now returned and I want data from the
old half, before it is resync'd back into the array.

I can start the old half as a new degraded mdadm array easily enough:
mdadm --assemble /dev/md3 --run --update=uuid /dev/sdc2

Of course, lvm complains about a duplicate volume group.  So I want to
rename and re-UUID the PV and VG.  I've tried

pvchange --uuid /dev/md3

But lvm refuses because the volume group name is "vg0" in the /dev/md3
metadata and vg0 is an active volume group on /dev/md1, the other half
of the RAID1.  (It seems lvm's check is slightly naive and it is just
looking at the name?)

How can change the metadata on /dev/md3 such that it can be activated
without interfering with the currently active VG of the same name and
uuid on /dev/md2?

I'm sure I've misunderstood something somewhere!

Aside, it's a bit alarming when the vg/pv related tools report "Found
duplicate PV <uuid>: using /dev/md3 not /dev/md1".  "Using" for what?
Will the system change to using the newly connected duplicate PV?  I
definitely don't want it to do that!


Thanks,
Richard

Re: [linux-lvm] How to start duplicate VG with new name and UUID?

[Bryn M. Reeves]

Richard Michael wrote:
> Hello list,
> 
> I'm using FC7 2.6.23.12-52.fc7 and LVM2 lvm2-2.02.24-1.fc7.
> 
> I have a RAID1 mdadm software array containing a VG.  Half the array has
> been removed from the system and now returned and I want data from the
> old half, before it is resync'd back into the array.

See:

http://www.redhat.com/archives/linux-lvm/2007-November/msg00039.html

And the reply from Alasdair which improves a couple of the steps.

Regards,
Bryn.

Re: [linux-lvm] How to start duplicate VG with new name and UUID?

[Richard Michael]

On Thu, Sep 18, 2008 at 10:22:01AM +0100, Bryn M. Reeves wrote:
> Richard Michael wrote:
> > Hello list,
> > 
> > I'm using FC7 2.6.23.12-52.fc7 and LVM2 lvm2-2.02.24-1.fc7.
> > 
> > I have a RAID1 mdadm software array containing a VG.  Half the array has
> > been removed from the system and now returned and I want data from the
> > old half, before it is resync'd back into the array.
> 
> See:
> 
> http://www.redhat.com/archives/linux-lvm/2007-November/msg00039.html
> 
> And the reply from Alasdair which improves a couple of the steps.

Thanks Bryn.  I actually did quite a bit of searching before posting,
and found your message you reference, but it wasn't applicable as your
first step was to deactivate the VG (and I can't deactive the existing
VG with mounted LVs).  But, I should have looked at Alasdair's reply,
which solves that problem.

Sorry for the noise, and thanks for pointing me to his reply, I'll give
it a go.

Regards,
Richard