IaaS vs PaaS vs SaaS
What the Three Cloud Service Models Mean
IaaS vs PaaS vs SaaS is the usual way to compare the three main cloud service models. IaaS (infrastructure as a service) provides basic computing building blocks. PaaS (platform as a service) provides a ready environment for running your code. SaaS (software as a service) provides a finished application.
The models differ in how much of the technology stack the provider runs for you. A typical stack has six layers: the data center and hardware, networking, the operating system, the runtime and middleware, the application, and the data. Each model moves the boundary between what the provider manages and what the customer manages.
Each model is covered in more depth in what IaaS is and what PaaS is.
Who Manages What in Each Model
The practical difference is the list of responsibilities that stay with you:
- IaaS: the provider runs the data center, hardware, virtualization and network. You install and maintain the operating system, middleware, applications and data.
- PaaS: the provider also runs the operating system and language runtime. You deploy your code and manage its configuration and data.
- SaaS: the provider runs nearly everything. You sign up, manage user accounts and settings, and store your own business data inside the application.
Email, customer relationship software and online office suites are common SaaS examples. Teams that want to ship applications without maintaining servers often choose PaaS. Teams that need full control of their operating system tend to choose IaaS.
A Small Online Shop Chooses a Model
A small online shop needs software to manage its orders. If it rents virtual servers and installs everything itself, it uses IaaS. It keeps full control, but it also patches the operating system and handles security updates. If it deploys its own code to a platform that handles servers and scaling, it uses PaaS and spends less time on operations. If it subscribes to a hosted order management product that the vendor runs, it uses SaaS and gives up most customization in exchange for simplicity.
Frequently asked questions
Which cloud service model is cheapest?
There is no single cheapest model. IaaS can look inexpensive per unit of compute, but it usually requires the most staff time to run. PaaS trades some flexibility for less operations work, and SaaS typically charges a predictable subscription. The true cost depends on how much your team has to build and maintain.
Can a company use IaaS, PaaS and SaaS together?
Yes, and most organizations do. A company might use SaaS for email, PaaS for its customer-facing web application and IaaS for a legacy database that needs a specific operating system. The models are not exclusive choices. They describe different parts of the same system.