According to the National Institute of Standards and Technology (NIST), cloud computing is a model for enabling on-demand access to a pool of computing resources that can be provisioned and released with minimal effort.
Furthermore, NIST categorizes cloud computing into three service models: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). Each has distinct advantages and disadvantages that impact the information technology (IT) efforts of an enterprise as well as its business practices and finances.
As the CIO’s role evolves from pure IT service provider toward full partner in defining and executing enterprise strategies, you’ll find yourself navigating those pros and cons of cloud computing.
The Service Models
The spectrum of cloud computing service models ranges from IaaS to PaaS to SaaS, with subtle variations in between. These models can be understood according to the increasing levels of IT services that each provides, along with the concomitant increasing levels of control that the enterprise must relinquish to the cloud provider.
IaaS providers deliver virtual server environments to the enterprise, upon which the IT department deploys all of the software layers it chooses.
PaaS providers deliver similar virtual server environments, but preloaded with specific operating systems, database systems, and development environments, thus decreasing the amount of effort needed by the IT department in setting up and maintaining those layers, but restricting the environments’ use to development and deployment upon those layers.
SaaS providers deliver fully functional applications that are accessed by end users via thin clients like web browsers; they do not expose the underlying layers to the customers.
The spectrum of cloud computing service models offers an increasing collection of managed IT services with concomitant decreasing control and flexibility.
The three cloud computing service models all provide varying levels of economies of scale, impose varying degrees of vendor lock-in, and have their own issues with regard to systems integration among the various on-premise and cloud systems that are deployed. Furthermore, the suitability of cloud computing varies with regard to IT and business maturity.