A report about scalability of virtualization techniques:

SCALABILITY COMPARISON OF 4 HOST VIRTUALIZATION TOOLS (QUETIER B / NERI V / CAPPELLO F)

"Virtualization tools are becoming popular in the context of Grid Computing because they allow running multiple operating systems on a single host and provide a confined execution environment.  In several Grid projects, virtualization tools are envisioned to run many virtual machines per host.  This immediately raises the issue of virtualization scalability."

4 types of virtualization tools are discussed in the context of scalability:

• Processor Virtualization
• Kernel Replication
• Operating System Virtualization
• Resource Virtualization