Re: unbelievably bad performance: 2.6.27.37 and raid6

[Andrew Dunn <andrew.g.dunn@gmail.com>]

Thanks for the update Neil, good to have something to look forward to.

I am using Ubuntu 9.10, hopefully the new kernel will be incorporated
sometime in the near future. In the mean time I will back everything up
and create the ARRAY all over again.

Thomas Fjellstrom wrote:
> On Sun November 1 2009, NeilBrown wrote:
>   
>> On Mon, November 2, 2009 6:41 am, Thomas Fjellstrom wrote:
>>     
>>> On Sun November 1 2009, Andrew Dunn wrote:
>>>       
>>>> Are we to expect some resolution in newer kernels?
>>>>         
>>> I assume all of the new per-bdi-writeback work going on in .33+ will
>>> have a
>>> large impact. At least I'm hoping.
>>>
>>>       
>>>> I am going to rebuild my array (backup data and re-create) to modify
>>>> the chunk size this week. I hope to get a much higher performance when
>>>> increasing from 64k chunk size to 1024k.
>>>>
>>>> Is there a way to modify chunk size in place or does the array need to
>>>> be re-created?
>>>>         
>>> This I'm not sure about. I'd like to be able to reshape to a new chunk
>>> size
>>> for testing.
>>>       
>> Reshaping to a new chunksize is possible with the latest mdadm and
>>  kernel, but I would recommend waiting for mdadm-3.1.1 and 2.6.32.
>> With the current code, a device failure during reshape followed by an
>> unclean shutdown while reshape is happening can lead to unrecoverable
>> data loss.  Even a clean shutdown before the shape finishes in that case
>> might be a problem.
>>     
>
> That's good to know. Though I'm stuck with 2.6.26 till the performance 
> regressions in the io and scheduling subsystems are solved.
>
>   
>> NeilBrown
>>
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>>     
>
>
>   

-- 
Andrew Dunn
http://agdunn.net