Re: Upgrade from Ubuntu 10.04 to 12.04 broken raid6.

[EJ Vincent <ej@ejane.org>]

On 9/30/2012 3:22 PM, Mathias Burén wrote:
> On 30 September 2012 20:20, EJ Vincent <ej@ejane.org> wrote:
>> On 9/30/2012 6:04 AM, Mikael Abrahamsson wrote:
>>> On Sun, 30 Sep 2012, EJ wrote:
>>>
>>>> Fast forward to now, I've upgraded the system to 12.04 LTS and have lost
>>>> access to my array. The array itself is a nine (9) disk raid6 managed by
>>>> mdadm.
>>>
>>> What version of kernel for 12.04 were you running?
>>>
>>> If you didn't upgrade your kernel, you might have been hit by the bug
>>> described in:
>>>
>>> <http://neil.brown.name/blog/20120615073245>
>>>
>> Hello,
>>
>> I'm running the stock version of Ubuntu 12.04.0, using kernel
>> 3.2.0-23-generic.
>>
>> That link looks interesting-- I'm not sure if I triggered the bug how Mr.
>> Neil Brown describes it, but I definitely have symptoms on some (not all)
>> the disks of RAID level "-unknown-" and devices appearing to be spares.
>>
>> I'm hesitant to re-create the array again (using mdadm) because according to
>> that blog post, for RAID-6, the order of devices are important, and with
>> this being a 9 disk array and no record of device order in logs or from my
>> own memory, I have no idea what the proper order might be.
>>
>> I do know that 1) I was using metadata version 1.2, 2) the array was not
>> degraded and subsequently 3) no disks were missing.
>>
>> Am I over-estimating the importance of the order and should proceed with the
>> re-creation, or perhaps wait for Neil himself to weigh in the problem?
>>
>> Thanks for all the responses, much appreciated.
>>
>> -EJ
>>
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> Can't you just boot off an older Ubuntu USB, install mdadm and scan /
> assemble, see the device order?

Hi Mathias,

I'm under the impression that damage to the metadata has already been 
done by 12.04, making a recovery from an older version of Ubuntu 
(10.04), impossible.  Is this line of thinking, flawed?

Thanks,

-EJ
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