[Gllug] RAID superblock on /dev/sda2 appearing on /dev/sda

[John Edwards]

On Fri, Oct 15, 2010 at 02:58:33PM +0100, John Edwards wrote:
> On Thu, Oct 14, 2010 at 06:23:44PM +0100, John Edwards wrote:
> <snip> 
> > Reading the mdadm RAID superblock docs:
> > 	https://raid.wiki.kernel.org/index.php/RAID_superblock_formats
> > 
> > It appears that the current 0.90 superblocks are written towards
> > the end of the device. Could it be possible that the end of the
> > partition of very close to the end of the disk and so the two
> > are getting confused?
> 
> This looks to be the case.
> 
> I've wiped the disks and then reinstalled with the partitions a few
> MB smaller than the end of the disk and the problem is not present.
> 
> There is a similar problem decribed in an obscure Debian mdadm FAQ:
>   http://git.debian.org/?p=pkg-mdadm/mdadm.git;a=blob_plain;f=debian/FAQ;hb=HEAD
> though I did not see that particular error message.
> 
> There are a couple of alternative fixes being to use 1.x superblocks,
> which can be positioned at different locations on the device, or
> specify the devices names in the mdadm.conf file.

For anyone still following this, it looks like the partition tool
in Ubuntu 10.04 tries to use every last KB of space, resulting in
an overlap of the superblock areas for partition and whole disk.

There is an existing bug report here:
    https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/599515


-- 
#---------------------------------------------------------#
|    John Edwards   Email: john at cornerstonelinux.co.uk    |
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