Re: [Xen-users] How many VMs on single server...

[Andy Smith <andy@xxxxxxxxxxxxxx>]

On Thu, Aug 23, 2007 at 07:07:24PM +0200, Alessandro R. wrote:
> > You will have no problem starting and running 14, 15, 20, 30, maybe
> > 100s of domains.
> 
> > Whether they have enough resources to do what you want them to do is 
> > another question.
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> I can't understand this paragraph. Can you explain?

OK, well say you have a server with 4G of RAM, and you start 15
domains with 256M RAM each leaving 256M for dom0.

Now you load an application on every domain that wants 512M of RAM.
All domains run out of RAM, work entirely from swap, this causes
massive disk IO across the whole server, load averages spiral
upwards and probably the whole machine becomes unusable for all
domains.

You have to spec each domain like any other server..

Cheers,
Andy

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