Re: Reopen: 16 HDDs too much for RAID6?

["Lars Täuber" <taeuber@bbaw.de>]

Hallo Bernd,

Bernd Schubert <bs@q-leap.de> schrieb:
> 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"?

I just wanted to make clear, that there couldn't be anything left anywhere on the disk. I already learned about this option of mdadm.

 
> > >
> > > 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

I just reassembled the array for another test. Next time I'll have a deeper look with this.


> 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?

Here the conf file:
monosan:~ # cat /etc/mdadm.conf 
DEVICE /dev/sd[ab][0-9] /dev/dm-*
ARRAY /dev/md2 level=raid1 UUID=d9d31de2:e6dbd3c3:37c7ea09:882a64e5
ARRAY /dev/md3 level=raid1 num-devices=2 UUID=a8687183:a79e514c:ca492c4b:ffd4384f
ARRAY /dev/md4 level=raid6 num-devices=15 spares=1 UUID=cfcbe071:f6766d8f:0f1ffefa:892d09c3
ARRAY /dev/md9 level=raid1 num-devices=2 name=9 UUID=db687150:614e76fd:28feefc0:b1aae572

All dm-* devices are really distinctive. I could post the /etc/multipath.conf too if you want.

Thanks
Lars
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html