If you're interested in making effective use of virtualization tools like Oracle VM Server, there's a whitepaper on oracle.com that you should check out.

The whitepaper starts with a few specific technologies and hardware: Oracle VM Server for SPARC, T4 Servers, Ops Center, Solaris 11, Sun Network 10GbE Switches, and Sun ZFS Storage Appliances. It then explains how to use them to plan and set up a virtualized environment, in which guests are grouped in Server Pools with high availability and are managed through Ops Center. It explains how Ops Center simplifies the management of logical domains by using custom plans to create new logical domains and managing their life cycle through its user interface.

So, if you're interested in setting up a cloud and you want to avoid surprises along the way, have a look.