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SubjectRe: Strange messages in my kernel log
On Wednesday August 30, avn@spylog.com wrote:
>
> I have strange messages in my kernel log (1-2 messages per day)
>
> raid5: bug: stripe->bh_new[2], sector 477640 exists
> raid5: bh 8ffd6da0, bh_new 8ffd63e0
> raid5: bug: stripe->bh_new[2], sector 6677320 exists
> raid5: bh aca1f060, bh_new aca1f720
> raid5: bug: stripe->bh_new[1], sector 6854048 exists
> raid5: bh b94c02c0, bh_new b94c0260
> raid5: bug: stripe->bh_new[2], sector 6889584 exists
> raid5: bh 833949c0, bh_new 83394d80
>
>
> What does it mean? Can this cause data corruption? Can i fix this problem?
> I use softvare RAID level 5, in kernel 2.2.16 with RH patches.

What does it means?

It means that raid5 received an IO request for a block of data for
which is already had an outstanding IO request. In these cases the
two i/o requests had different buffer_head strutures.
raid5 reports a bug, but actually handles the situation fairly
gracefully: it blocks the second request until the first has
finished.

Can this cause data corruption?

Not directly, but it might be a symptom of something else that could
cause corruption.

Can i fix this problem?

Maybe, but first we need to understand it.
The question is, how could there be two different buffer_heads for
the same block on disk?
My understanding of the 2.2 buffer cache is not very good, but I
think that all filesystems and block device IO go through the buffer
cache, so any of these accesses should never allow two buffer_heads
to point to the same block.
However I believe that swapping doesn't go through the buffer cache.

So: what are you doing with the raid5 partition.
What sort of file system?
Are you swapping to a file on the filesystems?
Is there any chance that a parity reconstruction is happening when
you get these messages.
Is there anything at all about your usage of the raid5 device that
could possibly be at all out of the ordinary?

>
> Or tell me, who mantain software raid code, and may help me solve this
> problem.

Well, Ingo Molnar <mingo@redhat.com> is the official maintainer, and I
have been doing a fair bit of development lately.

>
> Also I have second question.
> How much stable software RAID in latset 2.4.0 test series?

quite stable, but not very fast. RAID5 in 2.4.0 in particular is much
slower than 2.2.xx with mingo's patches. I'm working on this from
time to time.

NeilBrown


>
> --
> With best regards
> Alexander V. Nikolaev
> System administrator of spylog.com
>
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