In his blog "Clouds Are Only in the Sky" yesterday, Richard Martin suggested that a cloud must be on the public Internet for it to truly be a cloud and that if something resembling a cloud is used internally then it must be utility computing. He makes a very good point; however, I respectfully disagree.My explanation of private clouds and their value is explained in an entry from last week. In fairness, my focus often centers on the storage aspect of it and Rick's is across the entire cloud infrastructure.

While both private clouds and utility computing, and with it their storage counterparts, have similar capabilities and either term can easily be stretched to cover the other, private clouds and the companies creating the technology are emphasizing different aspects of the term. Private clouds share a public cloud's offering significant focus on being distributed. This distribution can be across geographies and across components within the platform. This distribution can be achieved by simple multisite replication like that done by cloud specific platforms from Parascale and Bycast, traditional archive platforms like Permabit and Copan Systems or altogether new concepts in distribution of data via block dispersion similar to what Cleversafe is performing. Private clouds share a public cloud's focus on simple, massive, and linear scalability by merely adding additional components to an active environment. Another focus in most cases is to use standard "off the shelf" hardware that is either then virtualized or in some sort of multinode grid. With additional components, scale will not only be delivered in additional capacity, but also in additional compute. In fact, one of the battle lines of cloud storage in particular is should you scale both capacity and performance in the same module or should you granularize further and allow specific granularization of capacity or performance. The scale private clouds deliver will be far beyond what most people associate to utility computing. Finally, private clouds in many cases will be the result of a migration from a public cloud. It will be common as an organization grows to look at the costs associated with having a service outsourced and they may decide to bring that capability in-house. In doing so, they will likely want to keep the components of architecture that worked well while improving on the weak points. Keeping the term cloud will be a more logical and efficient way to communicate to the users of that service what is happening... "We still have our cloud...it is just behind our firewalls now." People will create private clouds similar to the way companies have created intranets. They like the implementation of the concept, they just want to keep it to themselves. Track us on Twitter: http://twitter.com/storageswiss.

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George Crump is founder of Storage Switzerland, an analyst firm focused on the virtualization and storage marketplaces. It provides strategic consulting and analysis to storage users, suppliers, and integrators. An industry veteran of more than 25 years, Crump has held engineering and sales positions at various IT industry manufacturers and integrators. Prior to Storage Switzerland, he was CTO at one of the nation's largest integrators.