Amazon Web Services evangelist Jeff Barr coined a new term last week for an old concept. Provisioning data center resources to handle sudden and extreme spikes in demand is nothing new, but Barr's hybrid application hosting model, which he calls "cloudbursting," goes a step further in combining both private data center resources and remote cloud resources such as Amazon Ec2, which provides resizable compute capacity in the cloud.

Barr came up with the term after noticing that most of the audiences of developers and system architects he talked to about cloud computing and Amazon Web Services generally contained a balance of "wild-eyed" cloud computing enthusiasts and more conservative skeptics.

"The conservative side advocates keeping core business processes inside of the firewall. The enthusiasts want to run on the cloud. They argue back and forth for a while, and eventually settle on a really nice hybrid solution. In a nutshell, they plan to run the steady state business processing on existing systems, and then use the cloud for periodic or overflow processing."

Barr goes on to describe a cloudbursting use case where Norwegian developer Thomas Brox Røst combined traditional hosting with an EC2-powered, batch mode page regeneration system on an academic event-tracking site that contained more than 600,000 highly interconnected pages. As traffic and content grew, serving up the pages dynamically became prohibitively expensive, so Røst decided to use an array of 25 Amazon EC2 instances in a "cloudburst" arrangement for static file generation and background processing jobs. The savings benefit from not having standby dedicated servers was immediate and lasting, Røst says. "A simple EC2 instance is priced at $0.10 per hour. This would cost us a total of $0.10 x 5 x 25 = $12.50 -- or roughly the price of a pint of beer in Norway." Which says a lot about the low cost of EC2 instances as well as the high price of Norwegian beer.

The Cloud Computing Vocabulary section of Google's Cloud Computing Wiki says that up until now cloudburst has been used only in a negative sense, namely to describe the failure of a cloud computing environment due to the inability to handle a spike in demand (c.f. Nicholas Carr blog entry, "Intuit's cloudburst frustrates customers"). Barr uses the word in more positive way to describe the dynamic deployment of an internal software application to a public cloud to address demand need. Cloud computing lingo is evolving rapidly and I'm inclined to think Barr's more positive and descriptive coinage will ultimately have greater currency.

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InformationWeek has written a "Guide to Cloud Computing" that details the cloud offerings and strategies of Amazon, Salesforce, Microsoft, and five other providers.