Message-ID: <1571f45804875514762f60c0097171e6@localhost>
Date:	Wed, 26 Aug 2009 14:12:42 -0400
From:	Andrei Tanas <andrei@...as.ca>
To:	Ric Wheeler <rwheeler@...hat.com>
Cc:	NeilBrown <neilb@...e.de>, <linux-kernel@...r.kernel.org>,
	<linux-ide@...r.kernel.org>
Subject: Re: MD/RAID: what's wrong with sector 1953519935?

On Wed, 26 Aug 2009 11:39:38 -0400, Ric Wheeler <rwheeler@...hat.com>
wrote:
> On 08/26/2009 10:46 AM, Andrei Tanas wrote:
>> On Wed, 26 Aug 2009 06:34:14 -0400, Ric Wheeler<rwheeler@...hat.com>
>> wrote:
>>> On 08/25/2009 11:45 PM, Andrei Tanas wrote:
>>>>>>> I would suggest that Andrei might try to write and clear the IO
>>>>> error
>>>>>>> at that
>>>>>>> offset. You can use Mark Lord's hdparm to clear a specific sector
or
>>>>>>> just do the
>>>>>>> math (carefully!) and dd over it. It the write succeeds (without
>>>>>>> bumping your
>>>>>>> remapped sectors count) this is a likely match to this problem,
>>>>>>>
>>>>>> I've tried dd multiple times, it always succeeds, and the relocated
>>>>> sector
>>>>>> count is currently 1 on this drive, even though this particular
fault
>>>>>> happened at least 3 times so far.
>>>>>>
>>>>>>

>>>  you need to set the tunable:
>>>
>>> /sys/block/mdX/md/safe_mode_delay
>>>
>>> to something like "2" to prevent that sector from being a hotspot...
>>
>> I did that as soon as you suggested that it's possible to tune it. The
>> array is still being rebuilt (it's a fairly busy machine, so rebuilding
>> is
>> slow). I'll monitor it, but I don't expect to see the results soon as
>> even
>> with the default value of 0.2 it used to happen once in several weeks.
>>
>> On the other note: is it possible that the drive was actually working
>> properly but was not given enough time to complete the write request?
>> These
>> newer drives have 32MB cache but the same rotational speed and seek
times
>> as the older ones so they must need more time to flush their cache?
>>
> 
> Timeouts on IO requests are pretty large, usually drives won't fail an IO
> unless 
> there is a real problem but I will add the linux-ide list to this
response
> so 
> they can weigh in.
> 
> I suspect that the error was real, but might be this "repairable" type of

> adjacent track issue I mentioned before. Interesting to note that just
> following 
> the error, you see that it was indeed the super block that did not get
> updated...

The relevant portions of the log file are below (two independent events,
there is nothing related to ata before the "exception" message):

[901292.247428] ata2.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6
frozen
[901292.247492] ata2.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0
[901292.247494]          res 40/00:01:01:4f:c2/00:00:00:00:00/00 Emask 0x4
(timeout)
[901292.247500] ata2.00: status: { DRDY }
[901292.247512] ata2: hard resetting link
[901294.090746] ata2: SRST failed (errno=-19)
[901294.101922] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[901294.101938] ata2.00: failed to IDENTIFY (I/O error, err_mask=0x40)
[901294.101943] ata2.00: revalidation failed (errno=-5)
[901299.100347] ata2: hard resetting link
[901299.974103] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[901300.105734] ata2.00: configured for UDMA/133
[901300.105776] ata2: EH complete
[901300.137059] end_request: I/O error, dev sdb, sector 1953519935
[901300.137069] md: super_written gets error=-5, uptodate=0
[901300.137077] raid1: Disk failure on sdb1, disabling device.
[901300.137079] raid1: Operation continuing on 1 devices.

[90307.328266] ata2.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6
frozen
[90307.328275] ata2.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0
[90307.328277]          res 40/00:01:01:4f:c2/00:00:00:00:00/00 Emask 0x4
(timeout)
[90307.328280] ata2.00: status: { DRDY }
[90307.328288] ata2: hard resetting link
[90313.218511] ata2: link is slow to respond, please be patient (ready=0)
[90317.377711] ata2: SRST failed (errno=-16)
[90317.377720] ata2: hard resetting link
[90318.251720] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[90318.338026] ata2.00: configured for UDMA/133
[90318.338062] ata2: EH complete
[90318.370625] end_request: I/O error, dev sdb, sector 1953519935
[90318.370632] md: super_written gets error=-5, uptodate=0
[90318.370636] raid1: Disk failure on sdb1, disabling device.
[90318.370637] raid1: Operation continuing on 1 devices.

And here's the story for linux-ide from the earlier messages:
> I'm using two ST31000528AS drives in RAID1 array using MD. I've had
several
> failures occur over a period of few months (see logs below). I've RMA'd
the
> drive, but then got curious why an otherwise normal drive locks up while
> trying to write the same sector once a month or so, but does not report
> having bad sectors, doesn't fail any tests, and does just fine if I do
> dd if=/dev/urandom of=/dev/sdb bs=512 seek=1953519935 count=1
> however many times I try.
> I then tried Googling for this number (1953519935) and found that it
comes
> up quite a few times and most of the time (or always) in context of
> md/raid.

Regards,
Andrei.
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