Re: RAID-6 with 3 missing disks

[Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>]

Hi Neil,

On Sun, May 05, 2013 at 12:58:27PM +1000, NeilBrown wrote:
> On Sat, 4 May 2013 18:30:06 +0200 Piergiorgio Sartor
> <piergiorgio.sartor@nexgo.de> wrote:
> 
> > Hi Rudy,
> > 
> > thanks for the answer, but as mentioned at the end,
> > "--force" assemby does not work.
> > Reason is, 7 disks complains 3 are missing and the
> > 3 missing are assembed, since their superblock does
> > not report errors.
> > Of course, 3 disks are not enough to assembly the
> > array, forced or not.
> 
> Details please.  "--examine" output of every device would be a good start.
> Output for "mdadm --assemble --force --verbose ....."
> would help too.

thanks for the answer.
As mentioned in a sequent post, I fixed it by hex editing
the superblock and restoring, in the 7 disks, the other 3
missing.

Anyway, I did not considered the "--verbose" option, thanks
for the hint.

Thanks again,

bye,

pg

> 
> NeilBrown
> 
> 
> > 
> > bye,
> > 
> > pg
> > 
> > On Sat, May 04, 2013 at 04:22:39PM +0000, Rudy Zijlstra wrote:
> > > Hi
> > > 
> > > I would start with mdadm assemble --force
> > > 
> > > Do not use create unless all else has failed
> > > 
> > > Cheers
> > > 
> > > Rudy
> > > ---
> > > Verstuurd met mijn BlackBerry van Vodafone
> > > 
> > > -----Original Message-----
> > > From: Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>
> > > Sender: linux-raid-owner@vger.kernel.org
> > > Date:	Sat, 4 May 2013 18:08:04 
> > > To: <linux-raid@vger.kernel.org>
> > > Subject: RAID-6 with 3 missing disks
> > > 
> > > Hi all,
> > > 
> > > I know this was probably already discussed, but
> > > maybe I need some refresh.
> > > 
> > > I've a 10 HDDs RAID-6 which, due to mishap (disks
> > > were disconnected accidentaly), has now 3 missing
> > > devices and cannot be assembled.
> > > The data should be OK, since no writes were occurring
> > > during the accident, so putting them together again
> > > should work.
> > > 
> > > As far as I know, one option is to create, with
> > > "mdadm -C" the array again, giving the disks in
> > > the proper order.
> > > 
> > > Since all HDDs are readable, I guess "mdadm -E"
> > > should return the role of each device.
> > > Is this correct for the creation order?
> > > 
> > > Second question is about the "Data Offset", since
> > > this array was created with an older version of
> > > "mdadm" and the data offset is very close to the
> > > superblock.
> > > As far as I know, new mdadm creates the data a
> > > bit far aways.
> > > Is there any way to specifiy the proper offset?
> > > 
> > > Finally, is there an alternative to "mdadm -C"
> > > or it is the only option?
> > > Forcing assembly does not work, but maybe there
> > > is another way to tell mdadm to really assemby
> > > the array, taking into account the superblock
> > > information, which are all readable.
> > > 
> > > Thanks a lot in advance,
> > > 
> > > bye,
> > > 
> > > -- 
> > > 
> > > piergiorgio
> > > --
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> > 
> 



-- 

piergiorgio