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On 12/23/2014 01:36 PM, Robert van Leeuwen wrote:
>> from above numbers it doesn't sound like storage node is the
>> culprit - 50% drop happens on compute node going from baremetal to
>> virtual. So I'm inclined to think it's a tuning of virtio (if that
>> is even possible).
> 
> Some tuning tips for kvm: http://www.linux-kvm.org/page/Tuning_KVM
> 
> We saw a major improvement using RAW vs QCOW2 (in theory this should
> be similar, however, when you need a high random IO throughput we did
> see major improvements in our setup with RAW)
> 
> On more thing to check is partition alignment. (not very likely for a
> recent OS)

thank you Robert. As it turned out - it was a bug in our nova.conf
template which specified virt_type as qemu instead of kvm.. I found that
out comparing line-by-line manually created VM XML on the same node
(that performed great) and the one generated by nova. d'oh!



-- 
Dmitry Makovey
Web Systems Administrator
Athabasca University
(780) 675-6245
---
Confidence is what you have before you understand the problem
    Woody Allen

When in trouble when in doubt run in circles scream and shout
     http://www.wordwizard.com/phpbb3/viewtopic.php?f=16&t=19330

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