Re: Reopen: 16 HDDs too much for RAID6?

[Bernd Schubert <bs@q-leap.de>]

Hallo Lars,

On Friday 28 March 2008 10:20:02 Lars Täuber wrote:
> Hallo!
>
> Lars Täuber <taeuber@bbaw.de> schrieb:
> > I zeroed out all physical devices completely:
> > # for DEV in /dev/sd[c-r]; do dd if=/dev/zero of=$DEV; done

why not simply "mdadm --zero-superblock $DEV"?

> >
> > Now the problem is gone. I don't know what really caused the problem.
> > Many thanks for your suggestions.
>
> The problem has occured again.
> I'm not sure what the cause was, but the duplicated superblock is there
> again. But the raid fell apart before. So I suspect this occurs only after
> the array was degraded. The discs are not defective so I tried to
> reassemble the array with the original discs again: monosan:~ # mdadm -A
> /dev/md4
> mdadm: WARNING /dev/dm-9 and /dev/dm-8 appear to have very similar
> superblocks. If they are really different, please --zero the superblock on
> one If they are the same or overlap, please remove one from the
>       DEVICE list in mdadm.conf.
>
> How can I extract the superblocks to check if they are really identically?


mdadm --examine /dev/dm-9
mdadm --examine /dev/dm-8

Do you have some kind of multipathing, which really could cause a identical 
superblocks on dm-9 and dm-8? Did you specify dm-9 and dm-8 in you 
mdadm.conf / assemble script or the real human readable lvm / multipath 
names?


Cheers,
Bernd


-- 
Bernd Schubert
Q-Leap Networks GmbH
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