I see that Tony Asaro, Chief Strategy Officer over at Virtual Iron, recently presented some interesting comments about what makes up true server virtualization in his blog. In his post, he points out that "The hypervisor is important and is useful for consolidating servers. But true server virtualization isn't just about consolidation. Rather it is about managing server environments." While he's on the right track, there's even more to the story than the combination of virtual machine software and management software for virtualized environments.
I've pointed out for quite some time that virtualization goes way beyond merely the use of virtual machine software. It consists of at least six layers of technology that may be used individually or together to create a logical environment that serves the needs of the organization better than a physical environment could.
Depending upon the organization's goals, a virtualized environment may also include access virtualization, application virtualization, other forms of processing virtualization than just virtual machine software, storage virtualization, network virtualization and management software for virtualized environments.
Tony is certainly correct that if the organization's requirements center on a consolidated, agile computing environment, the tool set selected may include virtual machine software and management software. It may, instead, be founded upon the use of operating system virtualization/partitioning software, such as that found in HP's HP-UX, IBM's AIX, Sun's Solaris or even through the use of products such as Parallels' Virtuozzo to accomplish the same ends without the need for virtual machine software. In many cases, the use of operating system virtualization would be more efficient than the use of virtual machine software.
What about the cases in which the goals are performance, scalability, availability/reliability or uniform access from anywhere? Then other tools need to be brought out of the IT designer's tool kit.
Although I can quibble about some of the details of the post, Tony's primary point is a good one. Organizations that take a broad view of virtualization typically create a better environment than those who select a tool and think that is what should be deployed everywhere for every problem always. I believe that Abraham Maslow made the point very well with the comment "When the only tool you own is a hammer, every problem begins to resemble a nail."