linux-kernel - Re: 3.10.1: echo repair > sync_action causes hang on RAID-1 (2 x SSD)

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Date:	Mon, 22 Jul 2013 09:02:57 +1000
From:	NeilBrown <neilb@...e.de>
To:	"Justin Piszcz" <jpiszcz@...idpixels.com>
Cc:	<linux-kernel@...r.kernel.org>, <linux-raid@...r.kernel.org>
Subject: Re: 3.10.1: echo repair > sync_action causes hang on RAID-1 (2 x
 SSD)

On Sun, 21 Jul 2013 06:26:55 -0400 "Justin Piszcz" <jpiszcz@...idpixels.com>
wrote:

> Hi,
> 
> When I run repair on an MD-RAID1 sync_action, the speed slows down and it
> stays like this (below) for hours.  
> 
> The system is then completely unresponsive to user input.  I have replaced a
> failing SSD; however, after a check, mismatch_cnt seems to increase over
> time.  When I run repair, the system freezes to user-input.  Has anyone else
> run into this issue with a RAID-1 volume (2 x SSD) using 0.90 metadata?
> Long ago I used to use this same configuration with two physical disks and
> there was never a problem.
> 
> Even though I left a root shell open, this has no effect to break the
> resync:
> # echo idle > /sys/devices/virtual/block/md1/md/sync_action
> 
> Every 1.0s: cat /proc/mdstat                            Sun Jul 21 06:15:38
> 2013
> 
> Personalities : [raid1]
> md1 : active raid1 sdc2[0] sdb2[1]
>       233381376 blocks [2/2] [UU]
>       [>....................]  resync =  0.0% (151616/233381376)
> finish=36171.5min speed=107K/sec
> 
> md0 : active raid1 sdc1[0] sdb1[1]
>       1048512 blocks [2/2] [UU]
> 
> unused devices: <none>
> 
> 10 minutes later:
> 
>       233381376 blocks [2/2] [UU]
>       [>....................]  resync =  0.0% (151616/233381376)
> finish=52219.3min speed=74K/sec
> 
> Where it hangs (151616) or elsewhere, has been different each time I watched
> it, it does not appear to be hanging at the same block each time.
> 

Hi Justin,
 this is a known bug.  Fix has been accepted into mainline for 3.11-rc2.
 Hopefully it will get into 3.10.3 (too late for 3.10.2).

NeilBrown

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