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Virtualization: Open Standards, Interfaces, and Formats

We’ve been touting the notion of open standards, specifications, and formats for quite a while now. I wanted to take an opportunity to re-derive the importance of this openness to the virtualization industry and give a brief update as to where things stand.


We’re all seeing two very strong trends in the virtualization industry; growing enthusiasm for the notion of virtual appliances and a rapidly growing ecosystem around the virtualization layer.

Virtual Appliances

First, virtual machines are becoming a preferred way of developing, deploying, and managing software. We’ve termed the combination of an application and its operating system in a virtual machine a “virtual appliance“, and these truly have the ability to change the way we all think about software.

For virtual appliances to achieve their full potential, openness in virtual machine-related interfaces is critical. The real promise is “any software on any virtualization layer”. We believe customers should be able to choose and/or purchase a virtual machine consisting of any application running on any operating system and then run it on their virtualization layer of choice.

This scenario requires openness in virtual machine disk format, software licensing policies, and operating system-to-hypervisor communication. Dan Chu addressed the first two areas quite nicely in his recent blog. We’re seeing growing openness around Microsoft’s VHD disk format, but are concerned that they may start restricting the use of these virtual machines to their own virtualization software.

Much has also been written about “paravirtualization”, a set of optimizations that an operating system can leverage when it knows it is running within a virtualized environment. As mentioned in a previous blog, the Linux community seems to be iterating quite nicely towards a public, open approach to paravirtualization. This will allow a paravirtualized Linux-based software stack to run equally well across a variety of virtualization layers.

Microsoft also has a paravirtualization approach known as “enlightenments” that it will take advantage of in future versions of Windows. There has been no public commitment to freely allowing non-Microsoft virtualization layers to take advantage of these optimizations. We of course think that this is not in the best interest of customers or of the industry as it can lead to customer lock-in, non-interoperable virtual machines, and ultimately reduced choice in virtualization solutions.

Virtualization Layer

The second trend in the virtualization industry is rapidly growing adoption and a corresponding growth in the eco-system around the virtualization layer itself. There are several instances of virtualization available today and surely there will be even more in the future. We have been focusing on two areas important in helping both customer and others in the industry more easily manage and make sense of the growing options.

First, effective management of the virtualization layer is key to realizing its operational benefits. Furthermore, as virtualization further penetrates the datacenter, more and more customers will want their existing tools to be aware of, and in fact leverage virtualization’s unique capabilities. To work towards open industry standards, VMware and many other key players in the virtualization space are active participants in the DMTF SVPC (system virtualization, provisioning, and clustering) subgroup.

Second, customers continuously ask for benchmarking tools to enable them to intelligently make choices as to which virtualization offering makes the most sense for them and which hardware configurations are most appropriate for their needs. We recently blogged about VMmark, an approach to virtualization benchmarking that we have worked on with several partners.  More importantly, we’re pleased that the SPEC organization will begin work on an industry standard version of such a benchmark.

In summary, we’re at a unique point in time in the industry and have a great opportunity to do things better. By focusing on open standards, interfaces, and formats in several critical areas, we have a chance to really take advantage of all that virtualization has to offer.


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