What Is X-as-a-Service?
X-as-a-Service (XaaS) is the generic version of the three cloud computing models: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS).1
The fundamental business model at the heart of XaaS is the service rental model. You rent what you need or want. Innovation and deployment are faster with lower maintenance costs.
What is Infrastructure-as-a-Service (IaaS)?
Infrastructure-as-a-Service (IaaS) refers to providing the fundamental building blocks of computing that can be rented: physical or virtual servers, storage and networking.1
This is the provisioning of what can be thought of as the hardware. You need it but you cannot do anything useful with it yet.
This layer is the foundation upon which the other services are built. Think of it as online shopping for computing with virtually instant delivery. Deployments are faster with lower maintenance costs.
The IaaS layer is what is being talked about when you here the terms public vs private cloud.
What is Platform-as-a-Service (PaaS)?
Platform-as-a-Service (PaaS) is the next layer up from IaaS. In addition to the infrastructure layer of servers, storage, and networking, addition tools and software are added. The additions would include operating systems, database management, middleware, (services provisioned to applications beyond the operating system), and development tools.3
This layer is primarily for developers and operational professionals. Very few business people interact with this layer. This is the layer where you put the code and it will run. This allows companies to build applications and solutions, with control over the parts, without necessarily having the technical expertise to put it all together.
What is Software-as-a-Service (SaaS)?
Software-as-a-Service (SaaS) is the user facing delivery of application-as-a-service. This is the version of cloud computing most people experience. The underlying hardware (infrastructure) and software (operating system) are irrelevant to the end user because the service is accessed using a web browser or app.
SaaS is a packaged service that looks the same to all users. You don’t control updates or upgrades – it just happens. There are often some level of customization or personalization, but the entire stack is managed for a third-party.