This is where cloud service models come into play. They define the three primary ways to consume cloud services: IaaS, PaaS, and SaaS.
What Are Cloud Service Models?
Cloud service models determine which IT components you consume “as a Service” over the internet. They are critical because they define how responsibilities are divided between the customer and the cloud provider.
This leads directly to the Shared Responsibility Model: Depending on whether you use IaaS, PaaS, or SaaS, responsibility for managing servers, operating systems, and applications shifts from the organization to the provider. Understanding these models is key to deciding whether you want full control (IaaS) or maximum convenience (SaaS).
Three Layers of the Cloud: IaaS, PaaS, and SaaS in Detail
Service models are built as layers on top of raw computing power, gradually increasing the level of responsibility delegated to the provider.
1. SaaS (Software as a Service): The Turnkey Workspace
SaaS represents the highest level of delegation. Applications are accessed over the internet, typically via a web browser or app. The provider handles everything—from the application and runtime environment to the operating system, physical servers, and storage.
The Network is the Computer.
– John Gage, 1984, Sun Microsystems
The philosophy behind SaaS is simple: The application runs in the cloud, and the browser becomes the central workspace. ChromeOS is a prime example of an operating system designed entirely for SaaS applications.
- Customer responsibility: Configuring and using the software.
- Benefit: Maximum simplicity, rapid scalability, and minimal IT management.
- Use case: Ideal for standardized business applications.
For example, if you want to outsource document management or archiving without any infrastructure overhead, managed SaaS solutions offer maximum flexibility and instant availability.
2. PaaS (Platform as a Service): The Developer’s Playground
PaaS is the middle layer, primarily aimed at developers. The provider delivers the platform and runtime environment (operating system, databases, middleware).
- Customer responsibility: Only the application and its data.
- Benefit: Developers can focus entirely on coding and testing without worrying about server or OS management.
- Use case: Rapid development and deployment of custom business applications (e.g., a new mobile app)
3. IaaS (Infrastructure as a Service): The Flexible Foundation
IaaS offers the lowest level of provider management. Here, you rent the basic infrastructure: compute resources (virtual machines), storage, and networking over the internet.
- Customer responsibility: Managing the operating system, middleware, and all applications.
- Benefit: Maximum flexibility and control; essentially renting a server room from the cloud provider.
- Use case: Migrating complex legacy systems to the cloud or building specialized test environments.
4. The Key Difference: The Shared Responsibility Model
To better understand the models, compare who is responsible for what:
| Component | On-premises (Vollständig) | IaaS | PaaS | SaaS |
| Applications & Data | Customer | Customer | Customer | Provider |
| OS, Middleware, Runtime | Customer | Customer | Provider | Provider |
| Servers, Storage, Network | Customer | Customer | Provider | Provider |
The choice depends on your organization’s strengths. For maximum control over the operating system, choose IaaS. If the focus is on core business, SaaS is the way to go.
- Learn more about Private Cloud
- Learn more about Hybrid Cloud
- Learn more about On-Premises
Choosing the Right cloud Model: Where to Begin?
Selecting the right cloud service model is a strategic decision:
- When IaaS? If your IT team needs full control over operating systems and network configurations (e.g., for complex migrations or specialized workloads).
- When PaaS? If you have an agile development team and want to accelerate innovation.
- When SaaS? If you need standard functionality (like ECM or DMS) and want to minimize IT complexity.
Bottom line:
Cloud service models – IaaS, PaaS, and SaaS – are the blueprint for digital transformation. They allow businesses to align IT resources precisely with their needs and clearly define responsibilities.
The flexibility of modern cloud models opens up countless opportunities to optimize business processes. IaaS offers maximum control over infrastructure, while SaaS delivers ultimate convenience for application use. These solutions integrate seamlessly into any cloud scenario and help organizations unlock the full potential of their chosen model.
