Re: Raid5 regression

[Goswin von Brederlow]

Phillip Susi <address@hidden> writes:

> After enabling raid debug output and then loading mdraid09.mod, I can
> see that it is scanning and detecting the superblock on both (hdx) and
> (hdx,msdos1).
>
> On 5/3/2011 10:33 AM, Phillip Susi wrote:
>> After upgrading an Ubuntu server from Maverick to Natty ( grub2 version
>> 1.99-rc1-13ubuntu3 ) the system no longer will boot. Grub complains
>> about the raid5 array:
>>
>> error: Found two disks with the index 0 for RAID md0
>> error: Found two disks with the index 1 for RAID md0
>> error: Found two disks with the index 2 for RAID md0
>> error: Superfluous RAID member (4 found)
>> error: Unknown filesystem
>>
>> This is a 4 disk raid5 array that mdadm still recognizes and looks fine,
>> with each disk having IDs 0 through 3 respectively. Despite the fact
>> that it complains about the raid, it still shows the LVM logical volumes
>> in the output of ls. The array is the sole LVM PV.
>>
>> Bug filed at https://launchpad.net/bugs/776422. Any hints on how to
>> proceed with debugging this? Is there a way to check what modules are
>> built into the core image from the rescue shell?

That is a problem mdadm has (had?) too. The problem arises when the
alignment of the partition and its size causes the metadata of the
partition to be also valid for the disk (as in the partition ends
exactly at the end of the disk).

One of the reasons not to use metadata at the end of the disk.

MfG
        Goswin