Re: mdadm error - superfluous RAID member
On Wed, Jun 13, 2012 at 4:37 PM, Steve Dowe <sd@warpuniversal.co.uk> wrote:
> On 13/06/12 19:56, Tom H wrote:
>> On Wed, Jun 13, 2012 at 2:41 PM, Gary Dale <garydale@rogers.com> wrote:
>>>
>>> For example, Squeeze has problems with booting from partitioned RAID
>>> arrays.
>>> After running update-initramfs and update-grub, I find that the UUID for
>>> the
>>> partitions has been replaced with the UUID for the array, so that the
>>> boot
>>> fails. This particular problem can be solved by fixing the UUIDs in
>>> grub.cfg.
>>
>> grub2 was patched about a year ago to boot from a partitioned mdraid
>> "/boot" but I don't know whether that change made it into squeeze.
>
> I have just found the GNU grub development mailing list discussion, here:
> https://lists.gnu.org/archive/html/grub-devel/2012-02/msg00003.html
>
> Although the symptoms are the same as the Debian bug
> (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=610184), I'm not sure
> whether the causes are.
>
> I believe, in my case, the cause is the one discussed in the GNU list,
> namely that grub couldn't accurately detect whether a partition of the whole
> disk was assigned for RAID use. In the developer's own words,
>
> "if you have < 64KiB between end of disk and end of partition the metadata
> is exactly in the same place for either if the whole disks are raided or
> only partitions. And no field which allows to distinguish those"...
>
> On that basis, and the fact that grub in squeeze 6.0.5 seemed to exhibit the
> problem, I decided to update the machine to testing/wheezy instead and see
> if the problem disappears.
>
> I can confirm that it has. The error message no longer appears at boot time
> and I don't need to intervene to get to my login prompt.
>
> For anyone reading this in the same dilemma, I'm not sure if things like
> this would get backported to squeeze or not - perhaps someone has an idea
> how to find out...
Since metadata 1.1 or 1.2 stores the metadata at the beginning rather
than at the end, perhaps using a partitioned mdraid device with that
metada works with squeeze.
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