Re: raid 5 mismatch_cnt errors

[Doug Ledford <dledford@redhat.com>]

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On 05/21/2010 12:40 PM, MRK wrote:
> On 05/21/2010 04:16 AM, Doug Ledford wrote:
>> On 05/20/2010 06:38 PM, Neil Brown wrote:
>>   
>>> On Thu, 20 May 2010 17:29:37 -0500
>>> Trey Scarborough<treys@locallinux.com>  wrote:
>>>
>>>     
>>>> Neil Brown wrote:
>>>>       
>>>>> On Thu, 20 May 2010 12:02:23 -0500
>>>>> Trey Scarborough<treys@locallinux.com>  wrote:
>>>>>
>>>>>
>>>>>         
>>>>>> I have a raid 5 array with 9 disks and I have a mismatch_cnt that
>>>>>> keeps
>>>>>> growing. This is causing file corruption on the underlaying file
>>>>>> systems
>>>>>> as well.  I can copy a group of 100 100mb files and then do a
>>>>>> md5sum on
>>>>>> them and 1-3 will be corrupt. If this is a drive that is bad is there
>>>>>> anyway to run a report on the count per drive that these mismatches
>>>>>> occur. I have run smarttools test and do not see one drive that
>>>>>> stands
>>>>>> out to be causing errors. Could something else be causing these
>>>>>> errors?
>>>>>>
>>>>>>            
>> While a bad drive is certainly a possibility here, this is precisely the
>> type of failure scenario that would make me suspect bad RAM,
>> motherboard, or CPU.  So I wouldn't rule those out as possibilities
>> either.
>>    
> 
> Could the cabling to the drive be causing this? (maybe failing or maybe
> it's partly disconnected)
> I don't remember at what point Linux is at implementing the checksums
> between the controller and the drive.

I don't know.  I'm not up on the SATA signaling details so I don't know
if it uses CRC on the signal, but I suspect it does and a bad cable
would cause failed requests.  But I wouldn't bet my house on it, so I
would ask some SATA gurus.


-- 
Doug Ledford <dledford@redhat.com>
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