Quoting the blog from SearchServerVirtualization 

Currently, there are three main styles of server virtualization, and each has its benefits and drawbacks, according to open source consultant and author Bernard Golden, a presenter at the Red Hat Summit, happening right now in San Diego.

His lowdown on the three ways to virtualize provides a handy guide to the options today. Following his list, I offer some links to definitions, how-tos, tips and news about each method.

By the way, besides being a resident expert on SearchServerVirtualization.com and SearchEnterpriseLinux.com Golden is president of Navica Inc., an open source consulting firm, and author of the new book, “Virtualization for Dummies”. Check out his views on server hardware for virtualization in this post.

Here are the top three ways to virtualize:

Virtualization style: Operating system (OS) “container” emulation
Examples: Solaris Containers; SWsoft
Pros: Efficient; does not require additional software
Cons: Isolation; dependent upon OS; limits version choice within guest OS types

Virtualization style: Hardware emulation
Examples: VMware Server; Microsoft Virtual Server
Pros: Relatively easy to install and use; true isolation of OS instances
Cons: Less efficient than paravirtualization

Virtualization style: Paravirtualization
Examples: Xen, VMware ESX, Microsoft Longhorn virtualization
Pros: High herformance; true Isolation of OS instances
Cons: Extra software layer; complex to install and administer

Read the original to find out more and get information on other articles to help with this subject, here.