[Users] openvz disk access performance

[Michael H. Warfield]

On Mon, 2009-01-19 at 14:49 -0500, openvz.org at jks.tupari.net wrote:
> According to 
> http://www.scribd.com/doc/4916478/comparison-of-open-source-virtualization-technology
> openvz has good network performance, but bad disk access performance.  Has 
> anything changed in the 4 months since that was posted?

	Wow...  Could they possibly chosen a more inconvenient format.  A slide
show in pdf fed through flash.  That was painful.  Can't even download
the pdf to just page through it without signing up for an account.  Man
that sucks.

	I'd like to see some independent validation of those numbers and the
methodology.  Some things in there don't seem to pass the smell test
(particularly wrt disk times) and I wonder how well managed things like
file system positioning (location within a disk) and fragmentation were
managed and controlled.  I would like to know if they ran each test from
a controlled partition (so the location on disk didn't vary) and rebuilt
the file system each time (to manage fragmentation).  But, even the dd
from /dev/zero to /dev/null seems rather wonky to me.

	I also find it hard to believe, just from personal experience, that Xen
would beat OpenVZ for anything.  I've run Xen and I have OpenVZ in
production.  I've got a couple dozen OpenVZ VM's running on a single
platform with virtually no major load average problem (400+ processes at
any one time) where VMware crushed the processor at less than a dozen
and Xen couldn't even keep up with that (no HW virtualization).

	They also show Xen outperforming VirtualBox (I would have loved to see
a VMware comparison in there as well) but that is totally contrary to my
experience both with an without HW virtualization (but I noticed they
were using HW virt for Xen and had it disabled for VirtualBox for at
least some of the tests...  Hmmm...).

	I have first hand hands on experience with VMware, VirtualBox, Xen
(with and without HW vt), OpenVZ, Linux-Vservers, and kvm.  Their
results are too at odds with my experience.

	Mike
-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
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