From: NeilBrown <neilb@suse.de>
To: Daniel Frey <djqfrey@gmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: mdadm forces resync every boot
Date: Wed, 10 Aug 2011 11:31:46 +1000 [thread overview]
Message-ID: <20110810113146.3667affb@notabene.brown> (raw)
In-Reply-To: <4E41D9EC.1070706@gmail.com>
On Tue, 09 Aug 2011 18:07:56 -0700 Daniel Frey <djqfrey@gmail.com> wrote:
> On 08/08/11 16:34, NeilBrown wrote:
> >
> > When there have been no writes for a little while, mdmon will notice and mark
> > the array as 'clean'. It will then mark it 'dirty' before the first write is
> > allowed to proceed.
> > On a clean shutdown of the array it will mark that array as 'clean'.
> >
> > But for you, the system shuts down with the array marked 'dirty'. This
> > suggests that on your machine 'mdmon' is being killed while the array is
> > still active.
> >
> > Presumably your root is on the IMSM RAID10 array? When the root filesystem
> > is marked 'read only' it will probably write to the filesystem to record that
> > a fsck is not needed. So the array will be 'dirty'. If you then halt before
> > mdmon has a chance to mark the array 'clean' you will get exactly the result
> > you see.
> >
> > If you arrange that the shutdown script runs
> > mdadm --wait-clean --scan
> >
> > after marking the root filesystem readonly, it will wait until all arrays are
> > recorded as 'clean'.
> >
>
> Neil,
>
> I see by the switches it is watching /proc/mdstat for updates, but /proc
> was likely unmounted earlier in the shutdown process, and root is now
> read-only.
It need /proc, /sys, and /dev (assuming udev).
There is really no point in unmounting any of these as they are virtual.
Unmount everything else, remount root readonly, then "mdadm --wait-clean".
However I would expect missing filesystems to cause an early failure rather
than a hang. If mdmon had been killed already that might cause a bit of a
hang, but it should be limited to 5 seconds.
Maybe run 'mdadm --wait-clean --scan' under 'strace' and see what it is
doing??
NeilBrown
>
> I've put it in the shutdown scripts and the system hangs on shutdown -
> I've traced the hang to the command I put in above `mdadm --wait-clean
> --scan`.
>
> Is it possible it's waiting for a write somewhere? I'm so close to
> having it working now...
>
> Dan
next prev parent reply other threads:[~2011-08-10 1:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-05 15:05 mdadm forces resync every boot Daniel Frey
2011-08-06 10:18 ` Erwan Leroux
2011-08-07 0:09 ` Daniel Frey
2011-08-08 23:34 ` NeilBrown
2011-08-09 19:34 ` Daniel Frey
2011-08-10 1:07 ` Daniel Frey
2011-08-10 1:31 ` NeilBrown [this message]
2012-09-13 1:11 ` Daniel Frey
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