--- On Sun, 24/1/10, Goswin von Brederlow <goswin-v-b@web.de> wrote:

From: Goswin von Brederlow <redacted>
Subject: Re: Fw: Why does one get mismatches?
To: Jon@eHardcastle.com
Cc: "Goswin von Brederlow" <redacted>, linux-raid@vger.kernel.org
Date: Sunday, 24 January, 2010, 23:13
Jon Hardcastle [off-list ref]
writes:

quoted

--- On Fri, 22/1/10, Goswin von Brederlow <goswin-v-b@web.de>

wrote:

quoted

quoted

From: Goswin von Brederlow <redacted>
Subject: Re: Fw: Why does one get mismatches?
To: Jon@eHardcastle.com
Cc: linux-raid@vger.kernel.org
Date: Friday, 22 January, 2010, 18:13
Jon Hardcastle [off-list ref]
writes:

quoted

--- On Tue, 19/1/10, Jon Hardcastle <jd_hardcastle@yahoo.com>

wrote:

quoted

quoted

From: Jon Hardcastle <redacted>
Subject: Why does one get mismatches?
To: linux-raid@vger.kernel.org
Date: Tuesday, 19 January, 2010, 10:04
Hi,

I kicked off a check/repair cycle on my

machine

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after i

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moved the phyiscal ordering of my drives

around

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and I am now

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on my second check/repair cycle and it

has kept

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finding

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mismatches.

Is it correct that the mismatch value

after a

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repair was

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needed should equal the value present

after a

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check? What if

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it doesn't? What does it mean if another

check

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STILL reveals

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mismatches?

I had something similar after i reshaped

from raid

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5 to 6 i

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had to run check/repair/check/repair

several times

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before i

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got my 0.

Guys,

Anyone got any suggestions here? I am now on

my ~5

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check/repair and after a reboot the first check is

still

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returning 8.

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All i have done is move the drives around. It

is the

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same controllers/cables/etc 

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I really dont like the seeming random nature

of what

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can/does/has caused the mismatches?

There is some unknown corruption going on with

raid1 that

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causes
mismatches but it is believed that it will never

occur on

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any used
block. Swapping is a likely cause.

Any swap device on the raid? Try turning that

off.

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If that doesn't help try umounting filesystems or
remounting RO.

MfG
        Goswin

Hello, my usual savior Goswin!

The deal is it is a 7 drive raid 6 array. it has LVM

on it and is not used for swapping. I have umounted all LV's
and still got mismatches, i run smartctl --test=long on all
drives - nothing. I have now dismantled the array and am 3/4
the way through 'badblocks -svn' on each of the component
drive. I have a hunch that it may be a dodgy SATA cable but
have no evidence. No errors in log, nothing on dmesg.

quoted

Is there any way to get more information? I am

starting to think this is more happened since i changed from
raid 5 to 6..... which i did < 1 month ago.

quoted

The only lead i have is that whilst doing the bad

blocks 1 drive ran at ~10~15MB/s whereas the rest are going
at ~30 i have another identical model drive coming up so i
will see if that one is slow too. But the lack of logging
info is not helpful and worrying! and the prospect of silent
corruption a big worry!

You did run a repair pass and not just repeated check
passes, right?
Check itself only counts the mismatches but does not
correct them.
If the raid is unused (vgchange -a n) and you do first
repair and then
check then that definetly should not find any mismatches.

MfG

        Goswin

Hello!

Yes, I have a simple script that first does a check, then if there are mismatches it does repair. I have then been manually rerunning a check and I keep getting mismatches. I goes like this 232, 8, 24, 8, 8, 16, 16, 24, 24, 8, 16, 24. But I have also done this manually and run several repairs in a row (assuming that will return 0 if no work is to be done)

Now the array is completely dismantled and I am running bad blocks on the drives but I am on the last 2 of the 7 drives and I still have no leads. No bad blocks, no offline uncorrectable, no pending sectors no dmesg errors no nothing. I have absolutely no leads what so ever.

The only thing i have left to try is a full Mem test and disconnect and reseat the additional sata controllers, oh and buy 7 new sata cables incase 1 is bad.

But it would be REALLY helpful to know on what drive the mismatches have occured.

Any help here would be gratefully received! I might even try converting the array back to raid 5 as i remember i had mismatches immediately after i converted from 5 to 6.


      
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