From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: RAID-10 keeps aborting
Date: Thu, 06 Jun 2013 11:36:36 -0700
Message-ID: <51B0D6B4.6030802@zytor.com>
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To: Joe Lawrence <joe.lawrence@stratus.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>, Dan Williams <dan.j.williams@gmail.com>, linux-raid <linux-raid@vger.kernel.org>
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On 06/06/2013 11:27 AM, Joe Lawrence wrote:
> On Wed, 5 Jun 2013 12:29:32 -0700 (PDT)
> "Martin K. Petersen" <martin.petersen@oracle.com> wrote:
> 
>>>>>>> "hpa" == H Peter Anvin <hpa@zytor.com> writes:
>>
>> hpa> Yuck, this suddenly got complex.  Perhaps WRITE SAME should simply
>> hpa> be disabled on raid1/raid10 until this can be addressed?  
>>
>> Yeah, maybe.
> 
> Martin, 
> 
> I'm looking at the changes in raid1.c and am confused as to why we did
> this in the first place (commit c8dc9c6):
> 
>         if (mddev->queue)
>                 blk_queue_max_write_same_sectors(mddev->queue,
>                                                  mddev->chunk_sectors);
> 
> for RAID1, aren't chunk_sectors always going to be zero?  (At least on
> my machine, /sys/block/md*/queue/write_same_max_bytes for all md RAID1
> devices are set to 0.)  This would have the effect of rendering
> bdev_write_same() always false for these MD devices.
> 

That presumably also explains why only RAID-10 seems to be affected.

	-hpa