Much discussion in the cloud computing world has focused on a simple question: Is a private cloud infrastructure worthy of the name? It's been posed in many ways, with some going so far as claiming that there is no such thing as a private cloud. Although discussions like these are all too common in many areas, the question really amounts to little more than counting angels dancing on pin heads. The key issue is whether private cloud-style infrastructure can deliver real benefits like public clouds can.

First, let's set out some definitions:

• The draft NIST definition, perhaps the best we have at this point, states that "Cloud computing is a pay-per-use model for enabling available, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, services) that can be rapidly provisioned and released with minimal management effort or service provider interaction."
• McKinsey's controversial discussion document tells us that there are four key benefits of the cloud: Faster time to market, creation of new value drivers, easier scale-out, and lower upfront IT costs. These benefits were independently demonstrated by Roman Stanek of Good Data, and serve as a roadmap for cloud success.
• Defining what is and isn't a private cloud can be difficult, but the word "private" gives some clues. Simply put, a private cloud is closed off, existing solely for a single organization's use.

One of the key value propositions for cloud computing is the transfer of expense from the capital (CAPEX) to the operational (OPEX) column. In other words, using a service (like, ahem, the Nirvanix SDN) means there is no hardware or software to buy, built, and maintain. A simple recurring cost replaces an entire set of in-house processes and equipment. This is impossible if one builds their own "private" cloud.

But does the loss of this important benefit really mean that public clouds are worthless? Not at all! Private clouds can still deliver some of the other benefits of cloud computing, especially for the largest organizations. Private and hybrid clouds can also serve as a gateway, allowing enterprise IT to become familiar and comfortable with cloud computing paradigms in a controlled environment. Some private cloud applications may eventually be migrated to shared or public cloud infrastructure, but others might remain in-house permanently.

Consider the case of private, shared, and public air travel. Many of the biggest companies maintain their own stable of corporate aircraft. This might seem foolish to the average person, or even the travel departments of medium-sized businesses, but the substantial expense might be offset by the convenience or increased productivity of private aviation. Cloud computing is similar: The average individual or organization will probably derive maximum benefit from sharing a public cloud infrastructure, but this should not preclude certain special cases where a private cloud will be called for.

This is not a zero-sum game. The concept of cloud infrastructure is so strong that we should all stop worrying if this or that definition stands up. The future is coming, and it includes transformed and virtualized private infrastructure as well as public cloud providers.

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