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RE: [Xen-devel] Haddrive Performance

To: "Marcus Hardt" <marcus.hardt@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Haddrive Performance
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Mon, 25 Jul 2005 12:15:11 +0100
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Thread-topic: [Xen-devel] Haddrive Performance
> I've ran some simple 'dd' read performance tests on 
> xen-2.0.6-stable, finding quite different results between 
> image backed domains and partition backed domains. The Image 
> backed domains are slightly faster than the partion backed ones.

Are you sure they were using similar parts of the disk? There can easily
by a 2x or even 3x performance difference between the outside and inside
edges of the disk.
> Also I not, that for more than two domains, running dd in 
> parallel, the performance (especially of the image backed 
> domains) drops dramatically below values I've measured using 
> xen-2.0.5-stable.
> Are you aware of this? Will it be resolved?

No, we're not aware of any difference between the two, though there were
some changes to the way requests were batched. It would be good if a few
people on the list could investigate and produce some detailed
experiemntal data.


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