Cloud computing has two distinctly different meanings. The first is simple: The use of any commercial service delivered over the Internet in real time, from Amazon's EC2 to software as a service offered by the likes of Salesforce or Google.
The second meaning of cloud computing describes the architecture and technologies necessary to provide cloud services. The hot trend of the moment -- judging by last week's VMworld conference, among other indicators -- is the so-called private cloud, where companies in effect "try cloud computing at home" instead of turning to an Internet-based service. The idea is that you get all the scalability, metering, and time-to-market benefits of a public cloud service without ceding control, security, and recurring costs to a service provider.
[ In IT today, the action is in the private cloud. InfoWorld's experts take you through what you need to know to do it right in our "Private Cloud Deep Dive" PDF special report. | Also check out our "Cloud Security Deep Dive," our "Cloud Storage Deep Dive," and our "Cloud Services Deep Dive." ]
I've ridiculed the private cloud in the past, for two reasons. First, because all kinds of existing technologies and approaches can be grandfathered into the definition. And second, because it smacks of the mythical "lights out" data center, where you roll out a bunch of automation, lay off your admins, and live happily ever after with vastly reduced costs. Not even the goofiest know-nothing believes that one anymore.
Yet, despite natural skepticism, the private cloud appears to be taking shape. The technologies underlying it are pretty obvious, beginning with virtualization (for easy scalability, flexible resource management, and maximum hardware utilization) and data center automation (mainly for auto-provisioning of physical hosts). Chargeback metering keeps business management happy (look, we can see the real cost of IT!), and identity-based security helps ensure only authorized people get access to the infrastructure and application resources they need.