Re: RAID-10 keeps aborting

[NeilBrown <neilb@suse.de>]

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On Mon, 10 Jun 2013 10:15:05 -0400 Joe Lawrence <joe.lawrence@stratus.com>
wrote:

> A few outstanding questions that I have, maybe Neil or someone more
> familiar with the code could answer.
> 
> Q1 - Is mddev->chunk_sectors is always zero for RAID1?

Not always.  But often.  It is largely ignored.  I think the only effect is
to round the size of the device down to a multiple of the chunk size.

> 
> Q2 - I noticed handle_write_finished calls narrow_write_error to try and
>      potentially avoid failing an entire device.  In my tests,
>      narrow_write_error never succeeded as rdev->badblocks.shift = -1.

Yes.  You would need a newer mdadm (from my git tree) to get badblocks.shift
to something else.

> 
>      I think this part of the bad block list code Neil has been working
>      on.  I don't suppose this is the proper place for MD to reset
>      write_same_max_bytes to disable future WRITE SAME and handling the
>      individual writes here instead of the block layer?

If a drive reports that WRITE SAME works, but it doesn't, then I'm not sure
that I can be happy about working with that drive.
If a drive has some quirky behaviour wrt WRITE SAME, then that should be
handled in some place where 'quirks' are handled - certainly not in md.


I've applied that patch below - thanks.

NeilBrown


> 
> Regards,
> 
> -- Joe
> 
> 
> From b12c24ee0fce802f35263da65d236694b01c99cf Mon Sep 17 00:00:00 2001
> From: Joe Lawrence <joe.lawrence@stratus.com>
> Date: Fri, 7 Jun 2013 15:25:54 -0400
> Subject: [PATCH] raid1: properly set blk_queue_max_write_same_sectors
> 
> MD RAID1 chunk_sectors will always be zero, unlike RAID0, so RAID1 does
> not need to worry about limiting the write same sectors in that regard.
> Let disk_stack_limits choose the minimum of the RAID1 components write
> same values.
> 
> Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
> ---
>  drivers/md/raid1.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index fd86b37..3dc9ad6 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -2821,9 +2821,6 @@ static int run(struct mddev *mddev)
>  	if (IS_ERR(conf))
>  		return PTR_ERR(conf);
>  
> -	if (mddev->queue)
> -		blk_queue_max_write_same_sectors(mddev->queue,
> -						 mddev->chunk_sectors);
>  	rdev_for_each(rdev, mddev) {
>  		if (!mddev->gendisk)
>  			continue;


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