Re: GPT Table broken on a Raid1

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On Sat, 22 Sep 2012 12:45:39 -0600 Chris Murphy <lists@xxxxxxxxxxxxxxxxx>
wrote:

> 
> On Sep 22, 2012, at 9:31 AM, John Robinson wrote:
> 
> > 
> > I don't think there's anything wrong here.
> > 
> > The kernel sees the whole discs, sda and sdb, and complains that the GPT partition table looks wrong becase the second copy isn't at the end of the discs. That's correct, at the end of the raw discs is the IMSM metadata.
> 
> OK so sda and sdb shouldn't have been partitioned in the first place, is what that tells me.
> 
> 
> > Don't try to change the partition tables on /dev/sda and sdb or you will damage the IMSM metadata.
> 
> Sounds like either imsm metadata is either not well designed for GPT, or it was intended to be placed on an unpartitioned disk in the first place. 

IMSM metadata is definitely intended to be placed on an un-partitioned disk.

The only real point of IMSM is to provide interoperability with other
implementations, whether the one for Windows (allowing dual-boot) or the one
in the bios (allowing boot-from-RAID5 etc).
Those other implementations use IMSM on the whole device, so it would be
pointless using mdadm/IMSM on partitions.

Note that I haven't really been following this thread, so I might have missed
the point.  I'm really just responding to that last sentence.

NeilBrown

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