Three ways to get a meal
You can cook at home: you buy the food, the cooker, everything. You can rent a kitchen: the room and the cooker are ready, but you bring the food and cook. Or you can go to a restaurant: they do it all, and you only eat and pay.
Cloud services work like this too. The more the provider does, the less you do.
Key words
| Word | What it means |
|---|---|
| IaaS | infrastructure as a service: you rent the machines and look after the rest |
| PaaS | platform as a service: you rent a ready platform and look after your own app |
| SaaS | software as a service: you use a finished app and look after your own data |
| Client | the customer who rents the cloud service |
| Provider | the company that owns and runs the cloud |
| Runtime | the software that runs a program once it is started |
| Middleware | software that sits between the operating system and an app |
| Virtualisation | making a software copy of something real |
| Operating system | the main program that runs a computer |
| Network | devices joined so they can share things |
| Virtual machine | a computer made of software that runs inside a real one |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can say who looks after each layer in IaaS, PaaS and SaaS.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
A service is built in layers
Every system has layers. At the bottom are the machines, the storage and the network. Above them sits virtualisation. Then come the operating system, middleware, the runtime, the application, and last the data and the user accounts.
In the cloud, the line between what the provider looks after and what the client looks after moves up or down. The three models are three places for that line.
Who looks after each layer
| Layer | IaaS | PaaS | SaaS |
|---|---|---|---|
| User accounts | Client | Client | Client |
| Data | Client | Client | Client |
| Application software | Client | Client | Provider |
| Runtime | Client | Provider | Provider |
| Middleware and operating system | Client | Provider | Provider |
| Virtualisation | Provider | Provider | Provider |
| Servers, storage and network | Provider | Provider | Provider |
The cells students fill in are left blank in this preview.
Check
Have a go
Check
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.