Virtualization and disk performance

[Benoit des Ligneris]

Hello,

We study quite extensively the performance of virtualized systems (mainly
open source but VMWare as well). Even if this is an aging report you can
find the key results here :
http://www.slideshare.net/bligneri/comparison-of-open-source-virtualization-technology
(note : this is only a presentation of a more complete M.Sc. in Computer
Science in French.).

We strongly recommend not to virtualize any file server if you expect some
load. Even VMWare with supported hardware and software stack can be a real
PITA : we had some very bad experience for one of our customer (40000+ users
and several TB of shared space). Virtualization does not play well with high
performance I/O and when you pay the premium for you nice SAN, Fiber
channel, switch, extra-powerful servers you can accept a small performance
drop but in our case stability problems are the real trouble and much worse
to diagnose and address.

For databases, results are in line with the precedent item : if intensive
I/O is expected and you want best performance and, once again, the best
stability then ... same analysis. Also, even if some benchmark exists for
virtualization, I strongly encourage you to use your own load as a benchmark
: this provide the more accurate results and limit surprises during
the roll-out.

Ben

On Wed, May 12, 2010 at 3:25 AM, David Peall <david at dnservices.co.za> wrote:

> On Wed, 2010-05-12 at 10:19 +0300, Imre Gergely wrote:
> > With KVM guest, is that performance measured using virtio? If not,
> > maybe
> > you could try that.
> >
> >
>
> With virtio using a block device I get:
> Throughput 45.2551 MB/sec  100 clients  100 procs  max_latency=27865.397
> ms
>
> --
> David Peall
> Domain Name Services
>
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>



-- 
Benoit des Ligneris Ph. D., CEO
Revolution Linux
http://www.rlnx.com/
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