On Wednesday 27 February 2008 19:07:52 Rob Malpass wrote:
> I'm interested in saving some space and power at home so I'm considering
> ditching my cluster and running one higher spec box with 4-6 virtual
> machines. Now here's the question - with limited funds - will the gain be
> worthwhile?
What sort of virtualisation? And why do you want to virtualise (as
opposed to having 1 machine doing everything)? There are many different
virtualisation products, and several different types of virtualisation.
With something like VMWare, which virtualises the hardware, you need
at least enough memory for each machine even if they're not doing
very much, since you have to assign memory when you start them.
If you're running the same OS on each box (you just mentioned Slackware),
then you could go for user-space virtualisation, using something like
Linux Virtual Servers. This uses one kernel instance, which virtualises
the process space, disc and network, so you can run different applications
on each machine. Each guest shares the host's memory, so are really light
weight if they're not doing much since they only use what they need.
I'm currently running 8 VMs on a 1.6GHz dual core Athlon with 2GB of memory,
with no issues. LVS has almost zero overhead for each guest, so I could
run dozens if I wanted. The limiting factor is the applications that
are actually being used. I'm curring two Tomcat servers, two MySQL
instances, a mail server and a media streaming server. About half the
guests are just used for testing and development, and don't do very
much most of the time.
> Obviously even without the speed
> issue, there's are the space and power gains from what apparently is known
> as "p2v".
In my experience, "p2v" is a VMWare tool that converts a physical
machine into a virtual machine.
> I'm not so much bothered how quick it is - but what I don't want to do is
> lash out on the new box to find it's not capable of the task. Running 6
> VMs on any box is presumably asking a lot (though I believe we can now buy
> CPUs with virtualisation technology built in).
Only true if you're doing hardware virtualisation. With user space
virtualisation, any modern machine should be able to cope with hundreds
of virtual guests, as long as they're not doing much.
--
Be seeing you, http://www.glendale.org.uk
Sam. Mail/IM (Jabber): sam@???
