Re: RAID-6 with 3 missing disks

[NeilBrown <neilb@suse.de>]

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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.

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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> 


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