Re: System freeze triggered by RAID 10 resync and high io

[NeilBrown <neilb@suse.de>]

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On Tue, 20 May 2014 23:24:36 +0200 christian.schwarz@posteo.de wrote:

> Hello,
> 
> I have an issue with stalling writes that within a few seconds 
> ultimately lead to a full system freeze. Since all writes fail once the 
> condition has been triggered, there is no log output. Also dmesg remains 
> without errors.
> 
> My setup is as follows:
> 
> md127 : active raid10 sda1[0] sdd1[3] sdc1[2] sdb1[1]
>        3907023872 blocks super 1.2 512K chunks 2 near-copies [4/4] 
> [UUUU]
> 
> Linux 3.14.2-hardened-r1 #4 SMP PREEMPT

Fixed by upstream commit

commit cc13b1d1500656a20e41960668f3392dda9fa6e2
Author: NeilBrown <neilb@suse.de>
Date:   Mon May 5 13:34:37 2014 +1000

    md/raid10: call wait_barrier() for each request submitted.


which will be in 3.15, and hopefully will appear in the next 3.14.y release
(it isn't in 3.14.4).

NeilBrown


> 
> Dell Poweredge T20 Server
> 
> 
> To trigger this condition, a resync of the array has to be running and 
> high disk IO needs to be performed in addition. The condition is 
> triggered regardless of the resync speed (tested with 1, 10 and 100 
> MB/s). I also tried different io schedulers and a non-preempt kernel.
> 
> 
> Someone else over at Fedora reported a similiar problem: 
> http://www.spinics.net/linux/fedora/fedora-kernel/msg05163.html
> 
> 
> How can I help with providing additional information so you can locate 
> the problem?
> 
> 
> Thanks,
> 
> Christian
> 
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