Cloud Computing II – SS2 Digital Technologies Lesson Note (Third Term)

Cloud service models are the three layers into which cloud services are divided: IaaS (Infrastructure as a Service), PaaS (Platform as a Service) and SaaS (Software as a Service). With IaaS you rent raw hardware, with PaaS you get tools to build apps, and with SaaS you simply log in and use finished software.

Behavioural objectives

By the end of the lesson, students should be able to:

• State the full names of IaaS, PaaS and SaaS.
• Describe what each service model provides and who uses it.
• Give examples of each service model.
• Use the “Pizza-as-a-Service” comparison to explain who is responsible for what.
• State the advantages of cloud service models.

Who does the work in the cloud?

In our last lesson, we learned that “The Cloud” just means using someone else’s powerful computers over the internet. But not everyone uses the cloud in the same way.

Some people just want to use an app (like Instagram). Some people want to build an app. Others want to rent the whole computer to manage it themselves. To keep things organised, we divide cloud services into three layers.

What are the three layers of the cloud?

We call these the “Service Models”. Think of them as a pyramid.

1. IaaS (Infrastructure as a Service)

The Foundation: This is the most basic level. Here, you are renting the “raw” hardware: the servers, the storage and the networking.

• Who uses it? IT Administrators and System Architects.
• Your job: You have to install the operating system (like Windows or Linux), manage the security, and install all your software.
• Analogy: It’s like renting a bare piece of land. You have to build the house, put in the plumbing, and buy the furniture yourself.
• Example: Amazon Web Services (AWS), Microsoft Azure.

2. PaaS (Platform as a Service)

The Builder’s Tool: This is the middle layer. The cloud provider gives you the hardware and the tools (like databases and coding environments) to build apps.

• Who uses it? Software Developers.
• Your job: You only worry about the code for your app. You don’t care about how the server is cooled or how the hardware works.
• Analogy: It’s like renting a fully equipped kitchen. You don’t own the stove or the fridge, but you bring your ingredients and cook your own meal.
• Example: Google App Engine, Heroku.

3. SaaS (Software as a Service)

The Finished Product: This is the top layer and the one we use every day. The software is hosted on the internet, and you just log in and use it.

• Who uses it? End users (everyone).
• Your job: Just use the software. You don’t manage anything technical.
• Analogy: It’s like going to a restaurant and ordering a pizza. You don’t cook, you don’t clean the oven; you just sit down and eat.
• Example: Gmail, WhatsApp, Facebook, Netflix, Zoom.

What is the “Pizza-as-a-Service” comparison?

This is the easiest way to remember who is responsible for what.

What are the advantages of these models?

• Cost (pay-as-you-go): You don’t need to buy a ₦1,000,000 server. You can rent a small piece of one for ₦5,000 a month.
• Scalability: If your business grows from 10 customers to 10,000, you can just “dial up” your service level instantly.
• Mobility: You can access SaaS apps like Google Docs from a phone in Lagos or a laptop in London. Your work follows you.

How do IaaS, PaaS and SaaS compare?

Evaluation

1. If you want to start a new company and you don’t have money to buy hardware, which “As a Service” model would you choose?
2. Which model does Gmail fall under? Why?
3. Who normally uses each of the three models?
4. State the three advantages of cloud service models.

Assignment

Draw a pyramid in your notebook. Label the three layers (IaaS, PaaS, SaaS) and write one example of each inside the layers.