Re: IO failures with SMR drives at latest kernel versions

[Hannes Reinecke <hare@suse.de>]

On 08/26/2015 06:53 AM, Anatol Pomozov wrote:
> Hi
> 
> On Sun, Aug 23, 2015 at 11:15 PM, Hannes Reinecke <hare@suse.de> wrote:
>>> I looked at this commit and it actually adds SMR support to SCSI
>>> layer. Reverting ATA_DEV_ZAC means going back to zones-unaware
>>> algorithms. It is suboptimal but still much better than IO failures
>>> and "BTRFS: lost page write due to I/O error on /dev/sdc" errors I see
>>> at my computer.
>>>
>>> If this SMR support is considered as non-stable, can we at least get a
>>> kernel boot (or config) option that disables ZAC?
>>>
>> Again: Has anybody actually _tested_ that reverting this patch fixes
>> this issue?
> 
> Yes I tested it.
> 
> This error happens only under heavy load with a lot of read/writes
> (like btrfs rebalance).
> 
> With current Linux-4.1.6 'btrfs balance' fails after ~10 minutes after
> start. I reverted ZAC related changes and then ran rebalancing. The
> operation finished successfully after 3 hours of running.
> 
Can you be a bit more specific about the 'ZAC related changes'?
There have been several patches, and we really would need to know
which one was the offending one.
Can you try to bisect things here?

Thanks.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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