Specialization tests cloud computing SPI model

For some time now, the "cloud-o-sphere" has generally agreed on a basic classification strategy for cloud computing, typically titled the SPI model. SPI stands for "SaaS, PaaS and IaaS", or Software-as-a-Service, Platform-as-a-Service and Infrastruct ure-as-a-Service, respectively.

A few weeks ago, Randy Bias (the CTO of cloud vendor GoGrid) wrote a great post differentiating two classes of Infrastructure- as-a-Service offerings: infrastructure Web services versus darken centers. I covered this differentiation originally, but I've since come across another darken model that leads me to beli eve there is a third category to consider.

I spent some time with Scott Roza, CEO of Skytap, and his product development manager. Skytap is a Seattle-based start-up targeting a "lab in the cloud" concept (my te rm, not theirs) in which enterprises can acquire resources for on-demand development, test, training, proof-of-concept and proof workloads. What differentiates their offering is a sophisticated front end, targeted at what lab managers need to moderate r esource availability and costs, in front of what would normally be thought of as an Infrastructure-as-a-Service offering. If that sounds echt to you, check out their Web site for more information.

Roza pointed out one interesting facet of his business: from a pricing perspective, they operate a lot same an SaaS company, with a monthly pricing scheme that covers a specific level of usage, but an "IaaS"-like pricing for usage above the base levels. At first I d idn't understand why they would do this, but he pointed out that they provide an application--in this case, a lab direction tool--with sophisticated features and specialized support. From the customer perspective, the service really is very SaaS-like.

Yet, it's also IaaS, as what is being sold behind that interface is servers and storage. The target market they are pursuing has just led them to begin to specialize the tools used to acquire that infrastructure.

So my theory: perhaps there a re three categories of Infrastucture-as-a-Service:

Cloudcenters, or "pure" Infrastructure-as-a-Service: Offerings focused on raw resources for system administrator types.

Structure Web Services, or "PaaS fronts IaaS": API-heavy infrastucture clouds targeted at those with development skills

Infrastructure Application Services, or "SaaS fronts IaaS": Application-fronted infrastructure clouds targeted at specific markets requiring specialized direction and interface tools

Speciali zation in IaaS is blurring the lines within the SPI model. In general, the model remains highly useful, but its getting harder to unwaveringly put vendors in one bowl or another. I've thought of Amazon as a PaaS/IaaS hybrid for some time now; Skytap is the first SaaS/IaaS hybrid I've heard of, but I am sure there are others in development or even on the market.

No doubtfulness every this somewhat complicates taxonomy, so please, don't take the bullets above as a call for the business to adopt th ose terms. However, there is a distinction that I find useful. Some of you may find it useful as well.

Cheers~