[Gllug] Constrained virtual machines

[Daniel P. Berrange]

On Thu, Nov 30, 2006 at 03:05:11PM +0000, Richard Huxton wrote:
> Is anyone using VM technology that provides limits on CPU and I/O as 
> well as memory usage?

Xen gives you very good control over CPU scheduling of guests. Memory
is reasonable - you can balloon up & down guest OS memory on the fly.
With disk I/O there is near zero per-guest throttling / control, you
really have to rely on the Dom0 OS doing reasonably fair I/O scheduling.
Simiarly for network I/O, but at least for this you can use existing 
IP traffic shaping utilities in Dom0 if you need to control it based
on the MAC address of the guest OS.

> What I'd like to be able to do is run a set of database tests with 
> varying configuration settings. I'm not really concerned with absolute 
> numbers, but I'll need to scale CPU and I/O to generate some useful figures.

Xen will give you pretty good data for this - Database benchmarks are
a test we run very frequently for Xen on RHEL-5 to verify performance
is being maintained over course of development. Xen scales up quite
nicely as you add extra CPUs, or as you add increasing number of guests
doing same workload.

Make sure you use Xen 3.0.3 though - even just one minor release earlier
with 3.0.2 had absolutely terrible scalability.

Regards,
Dan.
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