July 7, 2021

Cloud Clarity: Differences Between IaaS, SaaS and PaaS Cloud Service Models

Chris Patterson

The general concept of cloud computing can be daunting enough, but then throw in the terms for cloud service models such as Infrastructure as a Service (IaaS), Software as a Service (SaaS) and Platform as a Service (PaaS), and things can get downright confusing.

What do each of these acronyms mean? How are they different? And how do you know which one is right for your company?

If you’ve asked yourself these same questions, then you’re in the right place—and clearer skies are ahead. In this blog, we break down the differences between IaaS, PaaS and SaaS, so you can make an informed decision about which of the cloud service models is best for your business.

Understanding the Three Cloud Service Models

The term “as a service” refers to a service delivered to a customer by a third-party provider, typically on a subscription basis. In the cloud world, there are three main service models: IaaS, SaaS and PaaS. Here’s a closer look at what those acronyms really mean.

1. Infrastructure as a Service (IaaS)

With the IaaS model, the cloud provider manages the IT infrastructures (this includes things like the server, storage or networking resources) and delivers them via virtual machines accessible through the internet.

IaaS infrastructures are usually like-for-like with on-premises environments, but instead of running applications on physical servers using physical firewalls, physical load balancers and other physical infrastructure components that you’re responsible for managing, you’re running them on virtual servers with your cloud service provider (CSP) delivering not only the virtual infrastructure but also accompanying virtual services.

The move to IaaS is relatively easy and cost-effective for companies to achieve because applications don’t have to be redesigned for the cloud—rather, they can be “lifted and shifted” into their new environment with minimal-to-no change. And once you’re up and running with IaaS, you can manage your new environment in much the same way as you did your on-premises infrastructures—so there is a minimal learning curve for IT teams.

Because it’s relatively easy for companies to transition to an IaaS infrastructure, and because of its similarities—both in design and management—with on-premises environments, this service model is often the first step companies take on their cloud journey. Therefore, it’s not surprising that it’s a popular service model today. According to Gartner, the IaaS public cloud services market grew by more than 40% in 2020 and reached a high of $64.3 billion.

The Pros and Cons of IaaS


  • IaaS gets companies out of the data center easily, quickly and cost effectively.
  • Companies can experience many of the benefits the public cloud has to offer, such as scalability and cost efficiencies.
  • In addition to being the easiest service model for companies to adopt, it’s also the model most traditional enterprise application vendors can support today.


  • Because infrastructure is shifted to the cloud in a like-for-like fashion—number of servers, databases, resource utilization expectations, etc.—organizations can’t take full advantage of the cloud’s cost-savings, performance and efficiency benefits.

2. Software as a Service (SaaS)

With SaaS, cloud providers host a complete application on their own cloud infrastructure and deliver it to end-users through the internet. Companies can access and use SaaS applications via a web browser, without having to install any infrastructure in their own cloud environment or worry about back-end maintenance (the cloud provider handles all of it). Salesforce, ADP (Automatic Data Processing Inc.) and Microsoft Office 365 are great examples of SaaS offerings.

SaaS applications are generally purchased on a subscription basis and packages are typically tailored to companies’ functionality needs or user requirements. For example, a company might purchase Salesforce for 50 salespeople. Or, a company might subscribe to a free SaaS offering for basic needs, but upgrade to unlock advanced features as business requirements change.

SaaS offerings are extremely prevalent within companies today because any employee can easily sign up for them—no cloud expertise needed. According to Gartner Inc.: “Software as a service (SaaS) will remain the largest market segment, which is forecast to grow to $116 billion next year due to the scalability of subscription-based software.” These numbers make sense when you think about all of the SaaS applications used by companies today—including collaboration tools such as Zoom, Dropbox, Slack and Microsoft Teams; email applications such as Office 365; and marketing tools, such as HootSuite, HubSpot and Salesforce. The list goes on!

The Pros and Cons of SaaS


  • Users can consume complete applications through the internet, without taking on the responsibility of infrastructure development, application management and overall IT maintenance.
  • Companies can achieve their business needs faster than if they had to implement and manage infrastructure on their own.


  • The SaaS model offers limited flexibility when it comes to application customization and control.
  • Because SaaS applications are easy for anyone to subscribe to, they often become part of “shadow IT”—applications downloaded without the knowledge or permission of the IT department—which can increase enterprise risk.

3. Platform as a Service (PaaS)

PaaS is a middle ground between IaaS and SaaS for running enterprise architecture, such as databases, web servers, etc. Unlike the IaaS model, where the company owns and is responsible for every aspect of deploying and running these infrastructure components on the cloud, only the necessary elements are presented via the cloud provider. For example, a company can deploy a database with just a few clicks, and the PaaS provider (AWS, Azure, Google Cloud) would be responsible for managing all the infrastructure behind it and most of the maintenance. In short, the cloud provider delivers the platform upon which companies can easily develop and scale out applications, without having to worry about cloud infrastructure management.

In some ways, PaaS is like SaaS for your infrastructure. Meaning, each part of the underlying cloud infrastructure required to run an application—servers, operating systems, storage services, databases, etc.—are individualized and offered as a service, which gives you the building blocks to easily build, deploy and scale your cloud infrastructure. This is important because it allows applications to run more efficiently and provides greater flexibility and increased time-to-deployment (upgrades and changes can be made directly to individual application components, rather than the entire application). In other words, you no longer have to worry about building or modifying database servers, application servers, web servers, etc., every time you want to make a change to your environment. Instead, you can simply log in to your CSP user console, click a few buttons and fulfill your request within minutes.

The Pros and Cons of PaaS


  • Developers can focus on application development, upgrades and enhancements rather than on infrastructure and maintenance.
  • Because applications are running on IT sanctioned cloud environments, application developers can maintain customization and control.
  • Companies can take advantage of cloud-native benefits such as scalability, speed-to-deployment and cost efficiencies.


  • While most enterprise application vendors have configured their applications to run on IaaS environments, many have yet to make them work with PaaS. This is why, to date, PaaS has been most useful for homegrown and customized applications.

Why PaaS is the Future

Today, many companies are running core enterprise applications (like SAP and Oracle, for example) in IaaS environments. As enterprise application vendors begin to make more ancillary infrastructure components compatible with PaaS, companies will follow suit—migrating them piece by piece from IaaS to PaaS services. For example, a company could have their core SAP application running in IaaS, but have associated file servers, Active Directory services and data warehousing tools running alongside it in PaaS.

PaaS is the ultimate end goal for custom and enterprise application vendors because it offers the greatest flexibility, scalability and efficiency of any of the cloud service models. And, with PaaS, you’ll realize the true functionality of the cloud. While most organizations will have a hybrid model of IaaS, PaaS and SaaS services for many years to come, we expect the IaaS/PaaS ratio to shift in favor of the latter, as more applications and application components are configured to run via PaaS services. 

Wherever you are on your cloud journey, Navisite is standing by to help. We support all major cloud service providers, and our dedicated cloud experts have years of cloud migration experience. We’ll help you assess your environment, build a customized migration roadmap, and efficiently migrate from on-premises to IaaS, SaaS and PaaS services. To find out how we can help your business, contact us today.

About Chris Patterson

Leveraging his technical background and consulting skills, Chris Patterson was a key player in building Navisite’s cloud computing platform, NaviCloud, from the ground up and is responsible for overseeing its continual upgrades and improvement making sure it meets clients evolving needs from both a technical and business perspective. In addition he oversees the development and implementation teams for Navisite’s Desktop-as-a-Service and NaviCloud Intelligent Storage solutions. Prior to joining Navisite, Patterson spent nine years at MTM technologies as the Director of Information Security Services, where he gained extensive experience developing and consulting on security policies in a variety of different industries including financial, retail, legal, health care, and public sector. Chris holds a Bachelors of Science in nuclear engineering from Worcester Polytechnic Institute and currently lives in Delaware.