𝑪𝒍𝒐𝒖𝒅 𝒔𝒆𝒓𝒗𝒊𝒄𝒆 𝒎𝒐𝒅𝒆𝒍

Cloud Service Models – IaaS, PaaS, SaaS

The chief advantage of IaaS, PaaS, SaaS or any 'as a service' solution is economic: A customer can access and scale the IT capabilities it needs for a predictable cost, without the expense and overhead of purchasing and maintaining everything in its own data center. But there are additional advantages specific to each of these solutions.

What are Iaas, Paas and Saas?

IaaS, PaaS and SaaS are the three most popular types of cloud service offerings. They are sometimes referred to as cloud service models or cloud computing service models.

IaaS (Infrastructure as a Service)

IaaS is on-demand access to cloud-hosted computing infrastructure—servers, storage capacity and networking resources—that customers can provision, configure and use in much the same way as they use on-premises hardware.

The difference is that the cloud service provider hosts, manages and maintains the hardware and computing resources in its own data centers. IaaS customers use the hardware via an internet connection, and pay for that use on a subscription or pay-as-you-go basis.

Typically IaaS customers can choose between virtual machines (VMs) hosted on shared physical hardware (the cloud service provider manages virtualization) or bare metal servers on dedicated (unshared) physical hardware. Customers can provision, configure and operate the servers and infrastructure resources via a graphical dashboard, or programmatically through application programming interfaces (APIs).

IaaS can be thought of as the original 'as a service' offering: Every major cloud service provider—Amazon Web Services, Google Cloud, IBM Cloud, Microsoft Azure—began by offering some form of IaaS.

PaaS (Platform as a Service)

PaaS provides a cloud-based platform for developing, running, managing applications. The cloud services provider hosts manages and maintains all the hardware and software included in the platform—servers (for development, testing and deployment), operating system (OS) software, storage, networking, databases, middleware, runtimes, frameworks, development tools—as well as related services for security, operating system and software upgrades, backups and more.

Users access the PaaS through a graphical user interface (GUI), where development or DevOps teams can collaborate on all their work across the entire application lifecycle including coding, integration, testing, delivery, deployment and feedback.

Examples of PaaS solutions include AWS Elastic Beanstalk, Google App Engine, Microsoft Windows Azure and Red Hat OpenShift on IBM Cloud.

SaaS (Software as as Service)

SaaS (sometimes called cloud application services) is cloud-hosted, ready-to-use application software. Users pay a monthly or annual fee to use a complete application from within a web browser, desktop client or mobile app. The application and all of the infrastructure required to deliver it—servers, storage, networking, middleware, application software, data storage—are hosted and managed by the SaaS vendor.

The vendor manages all upgrades and patches to the software, usually invisibly to customers. Typically, the vendor ensures a level of availability, performance and security as part of a service level agreement (SLA). Customers can add more users and data storage on demand at additional cost.

Conclusion

'As a service' refers to the way IT assets are consumed in these offering and to the essential difference between cloud computing and traditional IT. In traditional IT, an organization consumes IT assets—hardware, system software, development tools, applications—by purchasing them, installing them, managing them and maintaining them in its own on-premises data center.

In cloud computing, the cloud service provider owns, manages and maintains the assets; the customer consumes them via an Internet connection, and pays for them on a subscription or pay-as-you-go basis.

So the chief advantage of IaaS, PaaS, SaaS or any 'as a service' solution is economic: A customer can access and scale the IT capabilities it needs for a predictable cost, without the expense and overhead of purchasing and maintaining everything in its own data center. But there are additional advantages specific to each of these solutions.