During a presentation, I attempted to explain the differences between Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS) using examples to illustrate the resources provided by each:
- IaaS: VMware vCloud, Amazon EC2 (virtualization layer)
- PaaS: Amazon Web Services, Google App Engine (API or language for app building)
- SaaS: SalesForce, Google Docs (end-user software)
However, some of the participants didn’t understand the subtle differences between these different services. Luckily, I ran across Kate’s Comment blog’s graphical representation of the various layers that conveys where each of the *aaS services starts and stops. I’ve included it here so you can use it to help understand the difference and/or explain it to others.
IaaS, PaaS, SaaS Layers
I recommend starting from the bottom, where you will find the physical layers (power, networking, machines). From there it moves up into software and client devices/end users. On the right side, you will see where each of the *aaS (IaaS, PaaS, and SaaS) start and stop. For example, in IaaS, the cloud provider provides the data center, networking, physical servers, and a virtualization layer. The customer must bring their own OS, infrastructure, application software.
