--- On Fri, 22/1/10, 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: 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

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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

after i

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moved the phyiscal ordering of my drives around

and I am now

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on my second check/repair cycle and it has kept

finding

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mismatches.

Is it correct that the mismatch value after a

repair was

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needed should equal the value present after a

check? What if

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it doesn't? What does it mean if another check

STILL reveals

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mismatches?

I had something similar after i reshaped from raid

5 to 6 i

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had to run check/repair/check/repair several times

before i

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got my 0.

Guys,

Anyone got any suggestions here? I am now on my ~5

check/repair and after a reboot the first check is still
returning 8.

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All i have done is move the drives around. It is the

same controllers/cables/etc 

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I really dont like the seeming random nature of what

can/does/has caused the mismatches?

There is some unknown corruption going on with raid1 that
causes
mismatches but it is believed that it will never occur on
any used
block. Swapping is a likely cause.

Any swap device on the raid? Try turning that off.
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.

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.

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!


      
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