Cloud service models: IaaS, PaaS, SaaS

The service models define what you manage and what the cloud providers delivers. The National Institute for Standards and Technology defines three service models:

  1. Infrastructure as a Service, a.k.a. IaaS.
  2. Platform as a Service, a.k.a. PaaS.
  3. Application as a Service, a.k.a. SaaS.

You may find many references to other services models, like for instance Data as a Service (DaaS) or Blockchain as a Service (BaaS). However, those are only sub-models of the above three models, used generally by marketing departments or to attract attention on some services.

Service Models

To understand the three service models, we can go back to the way a server operates to deliver a service to a client. Between the network cable and the exposed application lies a set of hardware and services, as illustrated in the above figure. Adapted from the Open System Interconnection (OSI) communication model, you may find some variants, but the core idea remains the same.

If we start from the end user working with an application (the top of the figure), this application needs data to work. Application and data are enabled by a software and a middleware to abstract the operating system. This is what allows an application to work on different operating systems, like, for instance, Windows Server and Linux Red Hat. The operating system works generally in a virtualized environment. This allows to run multiple “logical servers” within a unique “physical server”. Virtualization has become mainstream with the increased power of physical servers. It allows to better use the power of the server resources and offers an increased flexibility to segregate different workloads. The physical server is linked to storage, generally now Solid-State Drives (SSD) to increase performance and reliability, and connected to a network.

If you are still confused by those models, then have a look at Matt Soseman Pizza as a Service model:

It’s all about who pays, who manages, and  who does what!

In next posts, we’ll look in details to each service models. Stay tuned and subscribe to the blog by providing your email address and clicking the Subscribe button!

Photo by Thomas Kvistholt on Unsplash

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