Cloud and Virtualization – SS3 Digital Technologies Lesson Note (First Term)

The cloud is storage and computing power that you reach over the internet instead of using your own device. The computers sit in large buildings called data centres. Virtualisation software splits one physical computer into several virtual machines, and remote servers let you use those computers from far away.

Behavioural objectives

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

1. Explain what the cloud is and give three reasons for using it.
2. Define virtualisation and describe it using the apartment building comparison.
3. Describe a virtual machine and state the work of a hypervisor.
4. Define a remote server and state its two main benefits.
5. Describe how the cloud, virtualisation and remote servers work together when we use a service like Gmail.

What is the cloud?

Many people think the “Cloud” is a magical place in the sky. It is not.

The Cloud is just someone else’s computer. Instead of saving a photo on your phone’s memory (local storage), you send it to a giant building full of powerful computers owned by companies like Google, Amazon or Microsoft. These buildings are called data centres.

Why use the cloud?

• Space: You do not run out of storage on your phone.
• Safety: If your laptop breaks, your files are still safe “up there.”
• Access: You can log in from any device in the world and see your work.

What is virtualisation?

In the old days, if a company needed a web server and a database, it had to buy two physical metal boxes (servers). This was expensive and wasteful because most of the time the computers were not working hard.

Virtualisation solves this problem. It is a piece of software that lets one powerful physical computer act like five or ten smaller computers.

The apartment building comparison

Think of a large house. Instead of one person living in the whole mansion and wasting space, we divide it into several apartments.

• The physical computer is the building.
• The virtual machines (VMs) are the apartments.
• Each person in an apartment feels like they have their own home, even though they share the same foundation and roof.

What is a virtual machine (VM)?

A virtual machine is a “computer inside a computer.” It is a software-based version of a physical computer. It has its own operating system (like Windows or Linux), its own memory and its own “hard drive,” but it does not exist as a separate piece of hardware.

What is a hypervisor?

The “manager” that creates and runs VMs is called a hypervisor. It sits between the real hardware and the virtual machines. It makes sure every VM gets enough RAM and CPU power without interfering with the others.

Common uses of VMs

• Testing a new app without damaging your main computer.
• Running Windows programs on a Mac.
• Running multiple websites on one single server.

What is a remote server?

A remote server is a computer that you access over a network, usually the internet. You are not sitting in front of it. It might be in Lagos while you are in Abuja, or it might be in London.

How do we talk to a remote server?

We use a “Remote Desktop” or a “Terminal.” You type on your keyboard, and the commands travel through the internet to the remote server. The server does the work and sends the “picture” of the result back to your screen.

Main benefits of remote servers

1. 24/7 power: Remote servers in data centres almost never turn off. They have backup generators and cooling.
2. Scalability: If your website suddenly gets a million visitors, you can “rent” more power from the remote server instantly.

How do the cloud, virtualisation and remote servers work together?

When you use a service like Netflix or Gmail, you are interacting with a remote server that is likely running on a virtual machine inside a cloud data centre.

The process flow

1. The hardware: A massive computer in a cold room.
2. The virtualisation: The computer is split into 100 virtual machines.
3. The service: One of those VMs is running the app you want to use.
4. The connection: You connect “remotely” via the internet.

Key terms

Evaluation

1. What is a data centre?
2. State three reasons for using the cloud.
3. In the apartment building comparison, what do the building and the apartments stand for?
4. What is the work of a hypervisor?
5. State two benefits of remote servers.

Assignment

In your notebook, answer these questions:

1. Explain the four steps in the process flow that happens when you use Gmail.
2. List two common uses of virtual machines.