- VirtualBox x64
- Two VMs of XenServer, each with 8 GB of RAM
- A guest OS of CentOS Desktop, one on each of the XenServers
- A VM of CloudStack via VirtualBox with 4GB of RAM, managing the XenServer servers
- Using XenCenter directly from the Desktop as another means of Managing the XenServers.
I'm pretty sure that's the beginning of a cloud right there, without ever having to leave 127.0.0.1.