linux-kernel - Re: SV: PROBLEM: raid5 just dies

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Date:	Tue, 31 Oct 2006 09:46:42 +1100
From:	Neil Brown <neilb@...e.de>
To:	"Andreas Paulsson" <andreas.paulsson@...arden.se>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: SV: PROBLEM: raid5 just dies

On Monday October 30, andreas.paulsson@...arden.se wrote:
> >Exactly how are aes-loop and raid5 connected together?
> 
> We use 5x300gb drives in a raid5 array, which is then used as a physical
> disk in an lvm volume, with one logical volume. This logical volume is
> then encrypted with "losetup -e aes /dev/loop1 /dev/vg0/lv0", and then
> formatted with ReiserFS.

Thanks.

It could be a hardware problem....
The symptom is that we try to free some memory and a consistency check
tells us that the memory wasn't allocated.  So a single bit error in
the address could be the cause.  Running memtest86 for a while
wouldn't hurt if you haven't already done that.

You have three layers here: loop over dm over md/raid5.
So if it is a software problem it could be in any of these layers, or
in an interaction between two of them.

1/ how repeatable is this?
2/ how much room have you got to experiment?
 Could you remake the array without the loop/aes and see if you can
 reproduce the problem?
 Could you remake the array without the LVM layer and see if you can
 reproduce the problem?

Do you have CONFIG_DEBUG_PAGEALLOC and CONFIG_DEBUG_SLAB set?  If not
could you recompile with those set to see if they provide more helpful
information. 

I must admit I am somewhat at a loss.  I cannot see much room for
problems leading to that particular point in the code that would not
be seen by lots more people than just you.

NeilBrown
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