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

[Luca Berra <bluca comedia it>]

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 comedia it
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