[Gllug] Constrained virtual machines

[Richard Huxton]

Richard Jones wrote:
> 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?
> 
> Be aware that disk performance under any VM I've seen sucks compared
> to the real hardware ...  So if you're testing a database, where disk
> I/O performance really matters, it's not clear the test will be fair.

Ah, but I don't care if disk access is 10 times slower than for-real. So 
long as I can then scale CPU and memory by the relevant amount to keep 
things balanced.

I'm not interested in absolute performance figures but the interplay 
between (virtual) hardware and database configuration.

As you point out, disk performance does seem to suck with VMs 
(understandable) which with an unconstrained VM would mean the effects 
of disk-cache would be out of proportion to the effects on a "real" server.

-- 
   Richard Huxton
   Archonet Ltd
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