Are Private Clouds an Abomination?

This is the question posted by Phil Wainewright in the Web 2.0 ebizQ forum where I am one of the panelists. Here's my answer:

A "private" cloud is just as much of a cloud as any other.

The typical private cloud is a cloud in which the cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on premise or off premise. Since all consumers of the private cloud are “trusted” (i.e. within the organization’s legal/contractual umbrella such as employees, contractors, & business partners), multi-tenancy, which is a big deal in the public clouds, becomes less of an issue.

However, a private cloud still satisfies the essential characteristics of what a cloud is.

NIST, for example, defines five essential characteristics of a cloud: On-demand self-service, Broad Network access, Resource Pooling, Rapid Elasticity, and Measured Service. Now consider the Cloud Security Alliance, which also defines the cloud in terms of five principal characteristics: Abstraction of Infrastructure, Resource Democratization, Services Oriented Architecture, Elasticity/Dynamism of Resources, and Utility model of Consumption & Allocation. Every other authoritative definition that I have come across defines the cloud in the context of similar essential characteristics. There is no reference to ownership of resources, sharing the cloud between organizations, competitors, across national or international boundaries, or the use of the public Internet as the backbone. It is because they are not essential characteristics of a cloud.

So, no, a “private” cloud is not an oxymoron. Would "public" cloud providers like us to believe so? Sure, but the fact is a private cloud is a necessity at times due to organizational maturity/capability/culture constraints, regulatory requirements, or SLAs that cannot otherwise be met.

Originally posted in the ebizQ Web 2.0 Forum on Septmeber 8, 2009.