Re: unbelievably bad performance: 2.6.27.37 and raid6

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

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.

NeilBrown