Re: Strange read data corruption on ext4/LVM/md

From: Pierre Ossman
Date: Thu May 20 2010 - 03:14:38 EST

(adding linux-ide)

On Wed, 19 May 2010 23:34:08 +0200
Pierre Ossman <pierre@xxxxxxxxx> wrote:

> I'm mostly talking to myself at this point, but one thing that occurs
> to me here is 4096 sectors line up decently with the numbers above.
> 0x380 is just at the end of a 512 byte sector, and 0xf80 is just at the
> end of a 4096 byte one. Not sure it's relevant, but then again I've
> stayed blissfully unaware of how this sector size transformation is
> going to happen. :)

Ignore the above. Math is hard.

I did some more testing though, and this might be a low level issue. I
did the following multiple times:

# dd if=/dev/sde skip=4k bs=4M count=500 | md5sum

And the results were:


Note that this is a live system, so there is some chance that something
wrote to than area, then restored it to the previous state. I'm not
sure how likely that is.

If not, then it would seem that this is a problem in either the disks,
the controller or the controller driver. The components are WD
WD1002FAEX, sil3132 and sata_sil24 respectively.

-- Pierre Ossman

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