What is virtualization?
Virtualization is used to describe many different technologies and approaches to abstract hardware from software. Server virtualization presents a virtual view of hardware to an operating system to allow multiple OSes to share the same physical resource in complete isolation from each other.

The x86 architecture was not originally designed for virtualization which created tradeoffs in early implementations in terms of both performance and complexity. Historically there have been two approaches virtualizing x86 architecture. Although both approaches create the illusion of physical hardware to achieve the goal of operating system independence from the hardware, there are significant differences between the approaches:

- Full virtualization with binary patching, at run-time rewrites the x86 instructions that cannot be trapped and converts them into a series of instruction that can be trapped and virtualized. Full virtualization is capable of running existing, legacy operating systems without modifications, however it has significant costs in complexity and runtime performance.

- Paravirtualization is where the operating system is modified to replace non-trappable x86 instructions with a series of calls directly into a hypervisor (a virtual machine monitor). It achieves high performance with less complexity in the virtualization layer but requires that the guest operating system to be substantially modified and tied to a particular version of the hypervisor. It also requires the users to upgrade to this new operating system and new applications.

What is native virtualization?
Native virtualization is a new approach that uses hardware assistance from recent Intel and AMD processors to eliminate the need for operating system binary patching or modifications while simultaneously providing the highest levels of performance. This allows customers to run any operating system version and workload.

Edited: 09/29/2006 at 06:19 PM by cbarclay