I have been in many conversations lately about Software as a Service (Saas) and Cloud Infrastructure & Technology. In those conversations I have found that there is commonly a mixing of what people think Saas and Cloud actually mean. In reality, there are two autonomous concepts and Cloud should not be used interchangeably with Saas.
Software as a Server, commonly shortened just called Saas is very descriptive of exactly what it means. With Saas there is a particular software application provided to clients via a service. That may be a bit confusing, so I will elaborate further. The software part of this acronym could be a calendar application, a to-do list, expense tracking, or something else. The delivery of that particular software is then provided by a service such as SOAP or REST Services, or some other transport medium over the Internet or other secure connection.
The other very significant implication of Saas is the process of payments for the particular software or service. This is the part that is not implied within the name. Saas is and was created primarily to allow creators of software to provide software based on subscription style payments. Since the maturity of software applications has reached a certain threshold the industry as a whole has been searching for a mechanism to allow more fluid and measurable means of revenue. Saas is the model that provides that means.
The Clouds Defined
What is cloud technology, infrastructure, applications, or computing? The various cloud offerings out there do not always work to provide a good clear definition of what exactly a cloud is. What I like to think of as the cloud ideal, which fits into most of the definitions is,
"Cloud Computing is Internet computing using shared resources over geographically dispersed areas. Over these areas, content delivery is provided with resiliency through redundant systems, drives, and other hardware providing a high uptime percentage (99.9% or more)."
Of course, that is my definition with my particular criteria that I feel is important to have for a legitimate cloud. As I learn and research more about cloud technology, infrastructure, and the ideals behind this model of computing I will most likely get more specific, and possibly add more to my personal definition of what Cloud Computing is. Also, see my original definition by real examples blog entry.
Cloud and Saas Clarification
The cloud, often used to describe a Saas model is incorrect. A Saas Business Model can be hosted in any number of cloud infrastructures, but one does not implicitly necessitate the existence of the other. A Saas Business Application may simply be hosted in a shared environment, or on a single server, partially clustered servers, or otherwise. Meanwhile a cloud infrastructure setup may not have any Saas Applications at all and instead runs only services between machines. Simply put, the cloud and Saas don’t particularly have anything to do with each other. It just happens that they often do.