|Cloud computing is a model for enabling remote, on-demand access to a shared pool of configurable computing resources. It comprises three service models: SaaS, PaaS and IaaS.|
Editor’s note: On May 8, Fermilab Today ran “Fermilab explores SaaS,” a blog post that originally appeared on the website "SaaS in the Enterprise." Fermilab Today readers wrote to ask the meaning of the acronym SaaS. A Fermilab visiting graduate student explains:
Software as a service (SaaS), platform as a service (PaaS) and infrastructure as a service (IaaS) are general terms used to describe the spectrum of internet services that companies and organizations can provide. These services are usually described as being in the “cloud” as they run remotely on the organization’s resources rather than the user’s computer. The spectrum ranges from IaaS to SaaS, with PaaS being somewhere in between the two. All of these terms are well defined by the National Institute of Standards and Technology document on cloud computing.
IaaS is the most basic of the spectrum of acronyms. In this service, the user rents computing resources such as processing power, storage space and networking using an interface such as a web browser. The user is able to configure the hardware and deploy and operate arbitrary software on these resources. Examples of IaaS providers are Amazon EC2 and Rackspace.
In PaaS, the user is provided with interfaces, programming languages, or other tools by the provider. The user has no control of the configuration of the underlying hardware supporting the application. Examples of PaaS are Google App Engine, Microsoft Azure and the Open Science Grid.
SaaS uses a provider’s software directly – the software runs entirely on the provider’s computers rather than the user’s. The user has no control of the underlying hardware or application. Examples of SaaS are Google Mail, Microsoft Office 365, and Fermilab’s FTL provided by Kronos.
—Derek Weitzel, University of Nebraska Holland Computing Center