I was thinking about holding off talking about standards and open interfaces until next time but they are an integral part of the discussion, thus here is an addition on that. Standards, specifications, and open interfaces are what will make it possible for the entire industry to fully leverage virtualization on the x86 platforms. There should be complete transparency and unconstrained availability (standards, open interfaces) of the interfaces between the hardware and the virtualization, the virtualization and the operating system, and the format of the virtual machines.

1. A virtual machine encapsulates an entire server or desktop environment in a file. The specification that describes and documents the virtual machine environment and how it is stored is critical to how virtual environments are provisioned, manipulated, patched, updated, scanned and backed up. VMware has made a specification virtual machine disk format called VMDK available for free without license and use restrictions.
   
   
2. The interface between the virtualization layer and the operating system. It is ideal for this interface to stay standardized and open so that all operating system environments can be supported. Bundled OS/Virtualization solutions suffer from two obvious risks:
   • The interface between the virtualization layer and the operating system will become complex and OS specific. This will make it more like an internal OS interface (like the Microsoft Windows Hardware Abstraction Layer) than a choice point. The interface will be optimized for the vendor's latest software and not other operating systems.
   • The interface will become a control point for the OS vendor. OS vendors have long enjoyed the control they get from being the first software installed on the hardware.
   VMware has identified a few key properties for the interface between the OS and virtualization layer, which we have documented as a set of concepts called VMI (Virtual Machine Interface). We have submitted an example implementation of these concepts to the Linux community, and we look forward to working with the Linux community (and other communities and industry vendors) to evolve the OS/virtualization interface into a form that is attractive for all parties, as well as fully open.
   
   
3. An API for managing virtual machines is needed so that all of the system management products can have one uniform way to manage all virtual machines. VMware has offered our API for managing virtual machines, developed and refined over the past 8 years. VMware is willing to support any API as long as it is functional to the full virtualization capabilities available in the market.
   
   
4. Benchmarks. There are starting to be multiple offerings for virtualization and the customer needs a way to evaluate the performance of the different offerings on apples to apples basis. There should be a benchmark that can show the performance in real-world relevant ways and also in a way that requires as inexpensive a setup as possible.