VM and performance (was Re: [Beowulf] best Linux distribution)

Olli-Pekka Lehto oplehto at csc.fi
Tue Oct 9 07:15:09 PDT 2007

Jeffrey B. Layton wrote:
> The recent emails from rgb and Doug lead me to a question. Has anyone
> tested codes running under a VM versus running them "natively" on
> the hardware (native isn't a good word and I hope everyone gets my
> meaning)?  The last word I heard is that performance takes a substantial
> hit if you are running a code in a VM. Some of the reasons are that the
> code has only virtualized access to the hardware (particularly the NICs)
> and memory management is a bit more difficult (although Barcelona with
> nested page tables should help there). I do remember VirtualIron saying
> that they had IB drivers so that the VM had direct access to the hardware.
> Thanks!
> Jeff

I ran some comparisons this spring on a small 4*2P AMD Opteron cluster 
using VMWare Player and Workstation. The results seemed quite promising 
and I'd like to share them but the VMWare EULA restricts the publication 
of unvetted results:

"You may use the Software to conduct internal performance testing and 
benchmarking studies, the results of which you (and not unauthorized 
third parties) may publish or publicly disseminate; provided that VMware 
has reviewed and approved of the methodology, assumptions and other 
parameters of the study. Please contact VMware at benchmark at vmware.com 
to request such review."

I just sent a request to VMWare about this. Let's see what they say...

Olli-Pekka Lehto, Systems Specialist, Special Computing, CSC
PO Box 405 02101 Espoo, Finland; tel +358 9 457 2215, fax +358 9 4572302
CSC is the Finnish IT Center for Science, www.csc.fi,
e-mail: Olli-Pekka.Lehto at csc.fi

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