[one-users] Opennebula and physical cluster

[dino]

hi. i've searched on all the net searching for a cluster solution that 
integrates perfectly in opennebula but i'm confused and i can't find a 
solution, i explain my problem (image this as a scenario), hoping you 
can recommend me the best solution:

i've 5 machines with 1gb of ram and 1cpu each.
i would like to do resource sharing with these machine, using opennebula 
to manage xen vm on the physical cluster, so 5 machines/nodes will be 
seen as only one machine with 5gb of ram and 5cpu, being able to create 
one huge vm with 4gb of ram (it is an example).
when i want to add resources, i will add another computer to the cluster.

is possible to do it or is a surreal scenario?

i just want that the cluster will be seen as a single node (and that the 
cluster supports xen).

i've readed about rocks cluster, sun grid engine, globus, quattor ecc 
ecc but which solution is totally transparent / integrates better with 
opennebula?

Best Regards,
Francesco