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

[Jelle Herold]

On Mon, Jun 14, 2010 at 10:41:19AM +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.
> > 
> > [snip]
> 
> 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?

I don't think this would work.

You need to design you application so that it can work in a distributed
fashion. Hypervisors don't (yet?) do this for you.

If your application is written in Java, then closest to what you want is
probably Terracotta, not sure how well this scales though.
http://http://www.terracotta.org/

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

Depends on what you mean by grid. But for instance SARA(.nl) and CERN
are testing opennebula based grids, see:
http://www.opennebula.org/:community:users
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