Re: unbelievably bad performance: 2.6.27.37 and raid6

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:
  

quoted

On Mon, November 2, 2009 6:41 am, Thomas Fjellstrom wrote:
    

quoted

On Sun November 1 2009, Andrew Dunn wrote:
      

quoted

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.

      

quoted

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.

  

quoted

NeilBrown

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Andrew Dunn
http://agdunn.net