[linux-lvm] vgdisplay - checksum error - what does it mean?

[Luca Berra]

On Fri, Feb 16, 2007 at 10:44:54AM +0100, Tomasz Chmielewski wrote:
>>>So this basically means, that LVM was set up on /dev/sda2 some time 
>>>ago, but it was never removed from there - instead, RAID-10 was set up 
>>>on that partition?
>>
>>I don't think so. if sda2 is part of a raid10 md array probably the
>>beginning sector of the md device maps to the beginning sector of the
>>real device, hence lvm will find an lvm signature on /dev/sda2.
>
>Is there a way to check if it's really the case?

dd?

>There's something wrong with /dev/sda2 - lvmdiskscan claims it's a 
>371.58 GB LVM physical volume, while /dev/md2 is the physical volume I use.
>
>   /dev/sda2                     [      371.58 GB] LVM physical volume
>   /dev/md2                      [      743.16 GB] LVM physical volume
>
>
>>>Should I do something to fix the things? What?
>>yes, re-enable md_component_detection in lvm.conf, why did you disable
>>that?
>
>Certainly I didn't touch anything in /etc/lvm/*.
>If I look into /etc/lvm/lvm.conf, it says:
>
>devices {
>(...)
>     # By default, LVM2 will ignore devices used as components of
>     # software RAID (md) devices by looking for md superblocks.
>     # 1 enables; 0 disables.
>     md_component_detection = 1
>}
>
>It's enabled.
>
>So the problem is somewhere else. Where?

with md_component_detection enabled lvm should ignore /dev/sda2.
can you send the output of lvmdiskscan -vvv?

>BTW, the machine is running Debian etch (ARM port).
mmm i don't have an arm maybe this is the issue why lvm does not
understand that sda2 is a md component?!?

>"smartctl" says all four disks are fine (they are quite new, too), so 
>it's definitely not a hardware problem.
sure it is not an hw problem do not worry.

>I guess one way to fix it would be mark all partitions faulty on 
>/dev/sda, and then, to recreate the RAIDs.
>But I'm curious to know how could I handle such a situation if I didn't 
>have RAID.
what would it fix? you have no problem except lvm2 believing sda2 is an
lvm volume which is not.

-- 
Luca Berra -- bluca at comedia.it
        Communication Media & Services S.r.l.
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