Cloud Essentials+ Journey – Cloud Service Models

So far in this series, we have covered a definition of the cloud and gone through the various cloud characteristics. In this post, we will get into the different ways cloud services can be delivered or consumed. These are known as the different cloud service models. Cloud service models describe what specifically is being delivered to the consumers, as well as which components are the responsibility of the cloud service provider and which components are the responsibility of the consumer. There are three main cloud service models out there with which to become familiar:

  • Software as a Service (SaaS)
  • Platform as a Service (PaaS)
  • Infrastructure as a Service (IaaS)

One key takeaway here is, as these service models are listed above, from top to bottom, the consumer has the least amount of responsibility with SaaS, and the most amount of responsibility with IaaS. Let’s dig into each of the above cloud service models.

Software as a Service (SaaS)
With the SaaS cloud service model, consumers are receiving a turnkey software solution. The software is hosted by the cloud service provider and the consumer merely has to connect to it with a client device and they are off the races. The CSP manages software updates and takes care of all of the underlying infrastructure (including compute, storage, networking, and facilities). As with many other things, there are trade-offs with SaaS. While you as the consumer have no responsibility for the underlying infrastructure, you also have no control over what that infrastructure is our how it is maintained. That being said, in my opinion, most of the the time that probably does not matter much. Examples of SaaS platforms include Google Workspace, Microsoft Office 365, and Cisco Webex. The main target market for Software as a Service applications is end users.

Platform as a Service (PaaS)
Platform as a Service moves the the consumer responsibility and control down a layer lower than Software as a Service. With PaaS, the consumer is provided with a virtual machine (VM), preloaded with an operating system and certain platform software. The consumer can interact with the VM/platform software on top of that VM operating system. While the consumer is responsible for running the platform software, they do not own responsibility of the operating system, virtualization layer, nor any of the underlying infrastructure. The target audience for PaaS is software developers and database administrators. The appeal to PaaS is that developers and database admins can focus on their core competencies without having to build and maintain the underlying VM and infrastructure. Examples of Platform as a Service offerings include Google App Engine, Heroku, and AWS Elastic Beanstalk.

Infrastructure as a Service (IaaS)
Infrastructure as a Service would be the closest thing to running virtual machines in your own data center. In fact, if you hear the term “lift and shift” in regard to migrating on-premises VM workloads to the cloud, IaaS is what would be in play here from the cloud service provider. With IaaS, the CSP delivers the consumer essentially a blank virtual machine. All of the underlying infrastructure, up through the virtualization layer is provided and supported by the CSP. The consumer is responsible for loading and maintaining the operating system and any software on top of the operating system. An important thing to remember here with IaaS (and any other cloud offering in which the user is responsible for software) is licensing. As a consumer, you are responsible for not only maintaining the OS and other software, but you are also responsible for ensuring all software is properly licensed. While you have the most control with IaaS as a consumer, you also have the most responsibility out of all the cloud service models. Examples of Infrastructure as a Service offerings include Microsoft Azure, AWS EC2, Rackspace, and DigitalOcean. The target audience for IaaS is IT/Systems administrators.

Cloud service providers definitely give us options to choose from when it comes to cloud services. It is important during the cloud assessment and cloud design phases to determine which model(s) make the most sense for you and your organization. Keep in mind that you might not leverage just one service model. You could run SaaS for your email and collaboration applications, PaaS for your development team, and IaaS for apps and servers that make sense to do so. Hopefully these interpretations made cloud service offerings less cloudy for you! (terrible pun, yes I know)

Published by Tim Bertino

Systems Architect passionate about solutions and design.

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