From: Neil Brown <neilb@suse.de>
To: Simon S <simon@sehier.fr>
Cc: linux-raid@vger.kernel.org
Subject: Re: reboot before reshape from raid 5 to raid 6 (was in state resync=DELAYED). Doesn't assemble anymore.
Date: Wed, 13 Oct 2010 07:46:12 +1100 [thread overview]
Message-ID: <20101013074612.6abbb698@notabene> (raw)
In-Reply-To: <20101012142752.GA16007@leontine.pompomgali.com>
On Tue, 12 Oct 2010 16:27:53 +0200
Simon S <simon@sehier.fr> wrote:
> Hi all,
>
> I had a config with 5 disks and 3 raid 5 arrays:
>
> md2 : system root
> md3 : swap
> md4 : data
>
> I added a 6th disk with the intention of growing my raid5 into raid6.
>
> The step I used were :
>
> # mdadm /dev/mdX -a /dev/newdiskX
> # mdadm -G --level 6 -n 6 /dev/mdX --backup-file /mdXbackup
> (yes, with backup file on root partition md2...)
Bad idea.. Very bad idea.
>
> The md3 array reshaped without any problem.
> md2 seemed to reshape well until it reaches 50.4%, then the rebuild speed stalled at 14Kb/s.
This is the expected consequence of that bad idea. Unfortunately it would be
hard to reliably get mdadm to complain about that, though I guess the common
cases are easy to protect against ... added to 'todo' list
> md4 was still in the state "resync=DELAYED" then.
>
> As the rebuild process seemed hung, I restart the machine ... bad idea.
Not really, nothing else would have worked.
>
> Now mdadm refuses to assemble md2 and md4, and displays this message :
>
> mdadm: Failed to restore critical section for reshape, sorry.
> Possibly you needed to specify the --backup-file
>
> md2 is my linux installation, not very bad if I lose this one.
>
> md4 however contains valuable data.
>
> While md4 was still in the state resync=DELAYED before the shutdown, I expect
> it should not has been (to much) modified and can be recovered.
Very true.
>
> Any idea on how I could safely do it ?
>
> Should I give a try to the hack "Get 'Grow_restart' to always return 0."
> mentionned by Neil Brown on 22 april 2010 in this mailing list ?
That is your best bet. I plan to make that easier to do in mdadm-3.2 (no
recompile necessary).
Before you do, check "mdadm -E /dev/newdiskX" and make sure the "Reshape
position" is 0. If it is you should be fine. I
It won't be for md2 of course. So md will quite possible have some
corruption. Run fsck on it an it will probably be mostly OK, but there is a
reasonable chance that some files will be corrupted. Whether and when you
will notice is impossible to guess.
NeilBrown
>
>
> Thank for any advices,
>
> Cheers,
>
next prev parent reply other threads:[~2010-10-12 20:46 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-12 14:27 reboot before reshape from raid 5 to raid 6 (was in state resync=DELAYED). Doesn't assemble anymore Simon S
2010-10-12 20:46 ` Neil Brown [this message]
2010-10-12 22:59 ` Simon SÉHIER
2010-10-12 23:06 ` Simon SEHIER
2010-10-13 0:08 ` Neil Brown
2010-10-13 8:18 ` Simon SÉHIER
2010-10-13 8:37 ` Neil Brown
2010-10-13 17:32 ` Simon SÉHIER
2010-10-13 20:24 ` Neil Brown
2010-10-14 8:35 ` [resolved] " Simon SÉHIER
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