[one-users] Can I use more hosts for just one VM?

[Daniele Fetoni]

First, thanks for reply.

I'm interested in this issue because, in my research lab, we want to create a cloud using a lot of  computer with max 2GB and 2 cores, and then deploy several (not just one or few like in a grid) VMs who requires more resources (such as 8 GB-8cores).

So we're interested in Opennebula capabilities.
Then I have more questions.
Reading your reply, I suppose this could be impossible because of the hypervisors used by Opennebula (Kvm, Xen). 
There is an hypervisor that could be useful for our purpose? For example, vmware can span multiple machines?

Opennebula has ever been tested for deploying and managing virtual machines in a grid?

Thanks again for kindness.

Daniele Fetoni

> Date: Fri, 11 Jun 2010 15:39:19 +0200
> From: jelle at defekt.nl
> To: daniele.fetoni at hotmail.it
> CC: users at lists.opennebula.org
> Subject: Re: [one-users] Can I use more hosts for just one VM?
> 
> On Fri, Jun 11, 2010 at 01:38:38PM +0200, Daniele Fetoni wrote:
> >
> > Maybe my question is stupid, but I found nothing in documentation, so
> > I want you to ask: is possible with opennebula create a VM using
> > resources from several hosts?
> >
> > I mean, if I have two cluster nodes with 2 cores each one, can I
> > deploy a VM requiring 3 cores?
> 
> No you can't, the underlying hypervisors (KVM,Xen) cannot span multiple
> machines.
> 
> This not suprising: cores need to talk to each other because they
> usually share state (memory, locks, etc). So, for this reason the
> communication channel between cores can become a bottleneck.  Bandwidth
> between two chips in a modern machine is extremely high: around 100
> Gbit/s or more! (Contrast this with a 1Gbit/s network).
> 
> Then there is latency and lots of other complicated issues, but you
> are entering grid-computing terrain here :-)
> 
> 
> Regards,
> Jelle.
 		 	   		  
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