MD1000-PERC5/E Performance issues

[Mike McGrath]

I've read up on:
http://thias.marmotte.net/archives/2008/01/05/Dell-PERC5E-and-MD1000-performance-tweaks.html

Which seems to have helped but I really don't think I'm seeing the
performance data I should be.  Take the attached sar data.  I started by
doing a recursive cp of some files from the filesystem to some other
drives, then started the sar dump.

At marker 12:12:55, I started to do a cat /dev/sde > /dev/null.  (/dev/sde
is the array).

Why was there such a significant jump there?  Also, why does sar think the
array was 100% utilized basically the whole time even though there's such
a difference in sec reads/s?

Other issues.  /dev/sde is the underlying physical device (raid5).
However, it is divided up using lvm.  The copy mentioned above was from
a logical volume.  While I expected some overhead and performance hit, I
didn't expect it to be so huge and sporadic.  I've seen reads as low as
3MB/s during a copy.

Thoughts?

	-Mike
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