Car, taxi or bus?
You need to get across town. You can rent a car: you drive, you choose the route, you buy the fuel. You can take a taxi: the taxi company does the driving and you only say where to go. Or you can take a bus: the company does everything and you only get on.
The cloud works in the same three ways. The more the provider does, the less you control.
Key words
| Word | What it means | Example |
|---|---|---|
| IaaS | Infrastructure as a Service. The provider gives you the computers, storage and network. You build the rest. | Rent a virtual server |
| PaaS | Platform as a Service. The provider gives you a ready platform to run your code on. | A place to deploy a web app |
| SaaS | Software as a Service. The provider gives you a finished program to use. | Online email |
| Client | The customer who uses the cloud service. | Your company |
| Provider | The company that runs the cloud service. | A large company that rents out servers |
| System software | The operating system and the middleware that applications run on. | Linux and a database server |
| Middleware | Software between the operating system and the application that helps them work together. | Software that links a web app to its database |
| Runtime | The software a program needs while it runs. | The Python interpreter |
| Virtualisation | Making virtual versions of computers and their parts. | Many virtual computers on one real computer |
| Operating system | The main program that runs a computer. | Linux |
| Network | Computers joined together to share data. | The internet |
The cells students fill in are left blank in this preview.
Who manages what?
| Layer | IaaS | PaaS | SaaS |
|---|---|---|---|
| Application software | Client | Client | Provider |
| System software (middleware and operating system) | Client | Provider | Provider |
| Runtime | Client | Provider | Provider |
| Data | Client | Client | Client |
| User accounts | Client | Client | Client |
| Virtualisation | Provider | Provider | Provider |
| Hardware: servers, network and storage | Provider | Provider | Provider |
The cells students fill in are left blank in this preview.
Quick check: who manages it?
Have a go
Quick check: who manages it?
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
IaaS: you build on rented machines
With IaaS the provider gives you virtual servers, storage and a network. You choose the operating system, install the software and look after updates.
You get the most control. But you also do the most work, and you need skills.
PaaS: you bring the code
With PaaS the provider also looks after the operating system and the runtime. You upload your application and your data.
Developers like it, because they can spend their time on code. The drawbacks are less control. Also, your app may only work on that platform.
Quick check: IaaS or PaaS?
Have a go
Quick check: IaaS or PaaS?
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.