So you have deployed virtualization, but do you have a private cloud?
What exactly is the difference between virtualization and private cloud computing? That is like asking, "What is the difference between blue and green?" When combined with yellow, the color blue makes the color green. Similarly, virtualization is simply one of the elements that makes cloud computing.*
To continue this analogue, cloud computing can happen without virtualization. Certain hardware, operating system and even application clusters can deliver cloud services. But these technologies can be complicated and costly, often requiring a lot of work to provide a limited set of features.
The more likely scenario is that a private cloud computing environment is built on a virtual infrastructure. Many organizations have deployed virtualization by creating virtual servers on top of their existing networking, storage and security stacks. But with private cloud computing, you need to think about and design these technologies in conjunction with one another.
In other words, you built previous virtual infrastructures on these stacks, but you need to build a private cloud with these stacks.
Virtualization as an element of cloud computing
Cloud computing is as much a methodology as it is a technology. You cannot plan any single element without considering the effect on the others. You also have to add in practices and policies that govern chargeback, monitoring, procurement and many other facets of your IT infrastructure.
For example, the ability to rapidly provision virtual machines does no good if it still takes six weeks to order and install a host server. Furthermore, procurement will always be a problem if chargeback is not recovering costs, and that requires resource and utilization monitoring. If your storage and compute resources have different provisioning schedules, they'll have to be documented and reconciled to properly forecast demand. I could go on, but your business requirements ultimately drive everything.
Private cloud computing does not center on virtualization or any one technology. It uses a set of technologies that have been aligned to be highly flexible and provide a wide range of services. This approach does not require virtualization, but virtualization does lend well to the core concepts of cloud computing.
Virtualization and cloud computing are also so closely connected because the major hypervisor vendors -- VMware, Microsoft and Citrix Systems -- are putting a lot of emphasis on the cloud. They have closely aligned their products with tools and complementary technologies that promote the adoption of private cloud computing.
Cloud computing is a rapidly evolving discipline, and one that will reshape org charts as fast as it will change data center layouts. It closely aligns with virtualization, but it takes many technologies to be successful.
*There is debate about whether green is a primary color. It takes blue and yellow to make green, but green occurs naturally. That is the reason for the competing CMYK and RGB color standards, and this controversy makes the analogy even more fitting.
About the expert
Mark Vaughn (MBA, VCP, BEA-CA) serves as an enterprise architect for a multinational corporation. Vaughn has more than 14 years of experience in IT as a Unix administrator, developer, Web hosting administrator, IT manager and enterprise architect. For several years, he has focused on using the benefits of virtualization to consolidate data centers, reduce total cost of ownership, and implement policies for high availability and disaster recovery. Vaughn is a recipient of the 2009 vExpert award and has delivered several presentations at VMworld and BEAWorld conferences in the U.S. and Europe. Read his blog at http://blog.mvaughn.us/.