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From: Neil Brown <neilb@suse.de>
To: Turbo Fredriksson <turbo@bayour.com>
Date: Sat, 30 Jun 2007 19:33:27 +1000
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Cc: Alasdair G Kergon <agk@redhat.com>,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Moving MD/LVM from PPC to x86
In-Reply-To: message from Turbo Fredriksson on Saturday June 30
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On Saturday June 30, turbo@bayour.com wrote:
> Quoting Alasdair G Kergon <agk@redhat.com>:
> 
> > On Thu, Jun 28, 2007 at 11:02:39PM +0200, Turbo Fredriksson wrote:
> >>   2. How do I move a VG/PV/LV from PPC to x86?
> >
> > The on-disk LVM2 metadata should be accessible from both
> > architectures.
> 
> Well, when I move the disks, the intel machine say that one of
> the disks don't have a partition table and that the other don't
> have any MD superblock...

Version 0.90 MD superblocks (still the default) uses host-endian
values so you cannot move between architectures directly.  However
isn't too hard to make it work. 
Firstly, use
   mdadm --examine --metadata=0.swap /dev/DEVICE

to check that you have the right devices.
Then

  mdadm --assemble /dev/md0 --update=byteorder /dev/DEV0 /dev/DEV1  ....

That should assemble the array and update the superblocks so that they
are in the right byteorder and will assemble easily in future.

NeilBrown