Why can a single physical server run Windows, Linux, and a web server all at the same time, as if they were separate machines? That is the problem that virtualisation and cloud computing solve: they decouple software from physical hardware. For the 220-1201 exam, you must understand how virtualisation works inside a hypervisor and how that relates to the three core cloud service models (IaaS, PaaS, SaaS) that businesses use today.
Jump to a section
A simple way to picture Virtualization and Cloud Computing
A single physical office building gets divided into many separate rented offices because a company needs to use the space efficiently and give each department its own private area. That office building is the physical server, the walls and floors are the hypervisor (the software that carves up the server), and each rented office is a virtual machine (a self-contained computer with its own operating system and apps).
Now take that idea and scale it up. Instead of one building, imagine a whole city of office buildings owned by a single company. That company decides it doesn't want to manage every light bulb, toilet, and elevator. So it hires a property-management firm. The firm handles all the maintenance, security, and cleaning. The original company simply pays a monthly fee and gets to use any office space it needs, whenever it needs it. That is the cloud — a giant pool of compute resources (servers, storage, networking) owned and managed by a provider (the property manager) and consumed on-demand by customers (the tenants).
The crucial insight: without the hypervisor dividing one physical server into many virtual machines, cloud providers could not pack hundreds of customers onto a single machine, and cloud computing would be wildly expensive and inefficient. The hypervisor is the essential innovation that makes the modern cloud possible.
Let's start with the core concept: virtualisation. Before virtualisation, if you wanted to run a web server and a database server, you needed two physical computers. Each physical machine had its own CPU, RAM, hard drive, and network card. That was expensive, wasted electricity, and took up floor space. If one server was only using 10% of its CPU capacity, the other 90% sat idle.
Virtualisation solves that by inserting a thin layer of software called a hypervisor directly on top of the physical hardware. The hypervisor's job is to carve the physical server's resources — CPU cores, RAM, storage, network interfaces — into multiple isolated, self-contained virtual machines (VMs). Each VM acts like a real physical computer. It has its own virtual CPU, virtual RAM, virtual hard drive, and virtual network card. You can install any operating system (OS) on each VM, like Windows Server, Ubuntu Linux, or even desktop Windows.
The hypervisor does not consume much of the physical resources itself. It is extremely lightweight. There are two types of hypervisors:
Type 1 hypervisor (bare-metal): This runs directly on the physical hardware with no underlying operating system. Example: VMware ESXi, Microsoft Hyper-V, KVM. It is more efficient and secure because there is no OS for an attacker to compromise. Data centres and cloud providers use Type 1 hypervisors almost exclusively.
Type 2 hypervisor (hosted): This runs on top of an existing operating system. Example: Oracle VirtualBox, VMware Workstation. You would use this on your laptop to test a different OS. It is less efficient because it has an extra layer (the host OS) that consumes resources.
Now, how does this relate to cloud computing? Cloud computing is the on-demand delivery of IT resources over the internet. Instead of buying and managing physical servers yourself, you rent compute, storage, and networking from a cloud provider like Amazon Web Services (AWS), Microsoft Azure, or Google Cloud Platform (GCP). The provider owns the physical data centres full of servers running Type 1 hypervisors. They use those hypervisors to create thousands of virtual machines that they rent to customers.
The 220-1201 exam focuses on three cloud service models, which define what you manage and what the provider manages:
Infrastructure as a Service (IaaS): The provider gives you virtual machines, storage, and networking. You manage the OS, middleware, runtime, data, and applications. The provider manages the physical hardware, hypervisor, and network. Example: renting an Amazon EC2 virtual machine.
Platform as a Service (PaaS): The provider gives you a platform — a pre-configured environment to develop and deploy applications. You manage only your application and data. The provider manages everything underneath (physical hardware, hypervisor, OS, middleware, runtime). Example: using Azure App Service to host a web app without managing the underlying server.
Software as a Service (SaaS): The provider gives you ready-to-use software over the internet. You manage nothing except your own data and user settings. The provider manages everything from physical hardware to the application itself. Example: Microsoft 365, Google Workspace, Salesforce.
Another key concept for the exam is the difference between public, private, and hybrid cloud:
Public cloud: Resources are owned and operated by a third-party provider and delivered over the internet. Multiple customers share the same physical infrastructure but are logically isolated from each other (multi-tenancy).
Private cloud: Resources are used exclusively by a single organisation. The cloud can be on-premises (in the organisation's own data centre) or hosted by a third-party provider. It offers more control and security.
Hybrid cloud: A combination of public and private cloud that allows data and applications to be shared between them. This is common for organisations that want to keep sensitive data on-premises (private cloud) but use the public cloud for burst capacity or development.
Finally, the exam tests cloud deployment characteristics including:
Elasticity: The ability to automatically add or remove resources (like VM instances) as demand changes. If your website gets a traffic spike, the cloud automatically spins up more VMs; when traffic drops, it turns them off.
Scalability: The ability to increase resources permanently to handle growth. You can scale up (upgrade to a bigger VM) or scale out (add more VMs).
Pay-as-you-go: You only pay for what you use. No upfront capital expense for hardware.
Resource pooling: The provider pools its computing resources to serve many customers, using multi-tenancy. Physical and virtual resources are dynamically assigned and reassigned according to customer demand.
Install a Hypervisor
To virtualise a physical server, you first install a hypervisor like VMware ESXi or Microsoft Hyper-V directly on the bare metal (Type 1). The hypervisor becomes the lightweight operating environment that will manage all VMs.
Allocate Physical Resources to the Hypervisor
The hypervisor detects the physical CPU cores, RAM, storage, and network interfaces. You then decide how to pool these resources — for example, assigning 4 of 8 CPU cores and 32 of 64 GB RAM to be used by VMs.
Create a Virtual Machine
Using the hypervisor management console (e.g., vSphere Client), you create a new VM. You define its virtual hardware: number of vCPUs, amount of vRAM, size of virtual hard disk, and virtual network adapter. This VM does not exist physically; it lives as files on the host server's storage.
Install an Operating System on the VM
You mount an ISO image (installation media) of an OS like Ubuntu Server or Windows Server to the VM's virtual DVD drive. You boot the VM. The VM sees the virtual hardware as if it were real hardware, and the OS installs normally. Now the VM is a fully functional computer.
Connect the VM to a Cloud Provider (Optional)
If you are building a private or public cloud, you now use orchestration software (like OpenStack) to pool resources from multiple host servers and expose them to users via a web portal or API. Users can then self-provision VMs, storage, and networking — that is the start of cloud computing.
Scale Out with Elasticity
In a cloud environment, you configure auto-scaling rules (e.g., CPU > 75% for 5 minutes triggers a new VM). When demand spikes, the cloud provider automatically provisions additional VMs from the resource pool. When demand drops, it tears them down. You only pay for the extra VMs while they are running.
Imagine you work as a junior IT administrator for a mid-sized company called GreenLeaf Organics. The company sells organic snack boxes online from a warehouse in Reading. Right now, GreenLeaf has two physical servers in a closet: one for the website and one for the customer database. The website is getting slow because more people are ordering, and the database server is almost out of disk space. The CEO says, 'Fix it, and do not spend thousands of pounds on new hardware.'
You decide to migrate to the cloud. Here is what you do, step by step:
First, you sign up for an AWS account (or Azure, or GCP — it does not matter). You go to the web console and create a virtual machine (EC2 instance, in AWS terminology). You choose an instance type: t3.medium (2 vCPUs, 4 GB of RAM). You select an operating system: Ubuntu Server 22.04 LTS. You configure the storage: 100 GB SSD. You set up a security group (a virtual firewall) to allow inbound HTTP (port 80) and HTTPS (port 443) traffic. The VM is ready in about two minutes.
Next, you install a web server like Nginx (or Apache) on that VM. You copy your website files from the old physical server using an SFTP tool. You point your domain name (greenleaforganics.co.uk) to the public IP address of the new VM. Now your website is running in the cloud. The old physical server gets repurposed as a test machine.
But the database server also needs to move. You provision a second VM for the database (e.g., MariaDB or PostgreSQL). However, you quickly realise that if that single database VM crashes, you lose all customer orders. So you set up a second database VM in a different AWS availability zone (a separate physical data centre in the same region). You configure database replication so that the second VM mirrors every transaction from the primary VM. If the first zone goes down, traffic automatically switches to the replica. This is called high availability.
Then the CEO says, 'What about Black Friday? What if our website gets fifty times more traffic than usual?' You explain elasticity. You configure an auto-scaling group: if CPU utilisation on your web server exceeds 75% for five minutes, the cloud automatically launches a second web VM and distributes traffic between both using a load balancer. When traffic drops, the extra VM is automatically terminated. GreenLeaf only pays for those extra VMs while they are running.
Later, you discover that developers at GreenLeaf want to build a new mobile app. Instead of giving them a full VM to manage, you provision a PaaS service like AWS Elastic Beanstalk. Developers just upload their code; the platform automatically handles provisioning, load balancing, and scaling. The developers love it because they do not have to think about servers.
Finally, you set up a SaaS service: Microsoft 365 for email and collaboration. Your users get @greenleaforganics.co.uk email addresses without you ever installing an Exchange server. You manage user accounts from a web portal. Everything just works.
Your manager is impressed. You have virtualised and migrated GreenLeaf from physical servers to the cloud, using IaaS (VMs for the website and database), PaaS (Elastic Beanstalk for app developers), and SaaS (Microsoft 365). You have implemented elasticity, high availability, and pay-as-you-go pricing. And you did it from your laptop, without ever entering a data centre.
The 220-1201 exam tests objective 4.1, which is titled 'Compare and contrast cloud computing concepts and virtualization technologies.' This means you need to be ready for questions that ask you to identify the characteristics of different cloud models and explain how virtualisation makes it all possible.
Here is exactly what the exam expects you to know:
Cloud service models (IaaS, PaaS, SaaS): The exam will give you a scenario describing what the customer manages versus what the provider manages. For example: 'A company uses a cloud service where they manage the operating system and applications. The provider manages the physical hardware and hypervisor. Which model is this?' The correct answer is IaaS. For PaaS, the customer manages only the application and data. For SaaS, the customer manages nothing except user data. They love to test the 'shared responsibility model' — what each party is responsible for.
Deployment models (public, private, hybrid): The exam asks you to differentiate based on who owns the infrastructure and who has access. Public = multi-tenant, third-party owned. Private = single-tenant, for one organisation. Hybrid = both public and private connected together. A common trap: they describe a scenario where a company uses its own data centre but uses virtualisation software to create a pool of resources. That is private cloud, not public cloud, even though it uses virtualisation.
Virtualisation concepts: You must know the two hypervisor types. Type 1 (bare-metal) runs directly on hardware. Type 2 (hosted) runs on an OS. The exam might ask: 'An administrator installs VirtualBox on a Windows 10 laptop to run a Linux VM. Which hypervisor type is this?' Answer: Type 2. Another question: 'Which hypervisor type is most commonly used in data centres for production workloads?' Answer: Type 1.
Elasticity vs. scalability: These sound similar but the exam distinguishes them. Elasticity is about automatically matching resources to demand in real time (think of a rubber band stretching and snapping back). Scalability is the ability to handle growth by adding more resources manually or automatically (think of adding another lane to a motorway). A question might say: 'A cloud workload automatically adds more web servers when traffic increases and removes them when traffic decreases. This is an example of which concept?' Answer: Elasticity.
Key cloud characteristics to know: On-demand self-service (users can provision resources without human interaction), broad network access (resources are accessible over the network from any device), resource pooling (provider serves multiple customers from shared physical resources), rapid elasticity, and measured service (pay-as-you-go metering).
Common exam traps: They will say 'A company buys a server and installs VMware ESXi. They create VMs for internal use only. Is this public cloud?' No, it is private cloud. They will say 'A developer uses a cloud service to deploy code without managing the underlying server. Is this IaaS?' No, it is PaaS. They will say 'A customer buys a month of uptime but the VM is only used for 10 hours. They still pay for the full month' — that violates pay-as-you-go, which should only charge for actual usage.
Memorise these definitions exactly:
IaaS = raw compute, storage, networking. You manage OS and above.
PaaS = platform to deploy apps. Provider manages OS and middleware.
SaaS = ready-to-use software. Provider manages everything.
Public cloud = multi-tenant, over the internet.
Private cloud = single-tenant, can be on-prem or hosted.
Hybrid cloud = public + private connected.
Type 1 hypervisor = bare-metal, runs directly on hardware.
Type 2 hypervisor = hosted, runs on an underlying OS.
Virtualisation decouples software from physical hardware by using a hypervisor to create multiple isolated virtual machines on a single physical server.
Type 1 hypervisors (bare-metal) run directly on hardware and are used in data centres; Type 2 hypervisors (hosted) run on an operating system and are used for desktop virtualisation.
Cloud computing delivers IT resources on-demand over the internet with pay-as-you-go pricing.
IaaS provides virtual machines, storage, and networking; you manage the OS and above.
PaaS provides a platform for deploying applications; you manage only your app and data.
SaaS provides ready-to-use software; you manage nothing except your own user data.
These come up on the exam all the time. Here's how to tell them apart.
Type 1 Hypervisor
Runs directly on physical hardware without an underlying OS.
More secure because attack surface is smaller.
Used in data centres and cloud providers (e.g., VMware ESXi, Hyper-V).
Type 2 Hypervisor
Runs on top of a host operating system (e.g., Windows, macOS).
Less secure because the host OS adds vulnerabilities.
Used for personal testing or development (e.g., VirtualBox, VMware Workstation).
Elasticity
Automatically adjusts resources up or down in real time based on demand.
Ideal for handling unpredictable traffic spikes (e.g., flash sales).
Resources spin up and down automatically without manual intervention.
Scalability
Adds resources manually or permanently to handle growth.
Ideal for planned growth (e.g., adding more storage over months).
Resources are added (scaling up/out) but not automatically removed when not needed.
Public Cloud
Owned by a third-party provider and shared across multiple tenants.
Accessed over the public internet.
Offers lower cost due to economies of scale but less control.
Private Cloud
Used exclusively by a single organisation.
Can be hosted on-premises or by a third-party but is logically isolated.
Offers more control and security but higher cost.
IaaS
Customer manages OS, middleware, runtime, data, and applications.
Customer provisions virtual machines, storage, and networking.
Example: Amazon EC2, Google Compute Engine.
PaaS
Provider manages OS, middleware, and runtime.
Customer manages only application and data.
Example: AWS Elastic Beanstalk, Azure App Service.
Mistake
Virtualisation and cloud computing are the same thing.
Correct
Virtualisation is the technology that creates multiple VMs from one physical server. Cloud computing is the business model that delivers IT resources on-demand over the internet, and it relies on virtualisation (among other technologies) to work at scale.
The terms are often used interchangeably in casual conversation, but the exam treats them as distinct. Many beginners assume if you have VMs, you have a cloud, which is not true.
Mistake
A Type 2 hypervisor is more secure because it runs inside a familiar operating system like Windows.
Correct
Type 1 (bare-metal) hypervisors are more secure because there is no underlying OS for an attacker to compromise. They have a smaller attack surface. Type 2 hypervisors add an extra layer (the host OS) that can be vulnerable.
It feels intuitive that adding a layer of abstraction would add security, but in computing, fewer layers generally mean fewer vulnerabilities.
Mistake
In a private cloud, the infrastructure must be on the organisation's own premises.
Correct
A private cloud can be hosted off-premises by a third-party provider as long as the resources are dedicated to a single organisation. The defining factor is single-tenant isolation, not physical location.
People confuse 'private' with 'on-premises.' The exam tests that private cloud is about exclusive use, not location.
Mistake
In PaaS, the customer is responsible for patching the operating system.
Correct
In PaaS, the provider handles the operating system, middleware, and runtime. The customer only manages their own application and data. Patching the OS is the provider's responsibility.
Many beginners who have used IaaS (where they patch the OS) assume all cloud models work the same way. The shared responsibility model shifts with each service model.
Reveal each answer, then mark whether you got it right. Score 60%+ to unlock the next chapter.
Virtualisation is the technology that allows one physical server to run multiple virtual machines. Cloud computing uses virtualisation (and other technologies) to deliver IT resources over the internet on a pay-as-you-go basis. You can have virtualisation without cloud computing (e.g., a single server running VMs in your office), but cloud computing always relies on virtualisation.
No, the exam does not test hands-on cloud configuration. It tests your understanding of cloud service models (IaaS, PaaS, SaaS), deployment models (public, private, hybrid), and virtualisation concepts (hypervisor types, VM characteristics).
It defines which security and management tasks are handled by the cloud provider and which are handled by the customer. In IaaS, the provider handles physical hardware and hypervisor; the customer handles OS, apps, and data. In PaaS, the provider handles OS and middleware; the customer handles only the application and data. In SaaS, the provider handles everything except customer data.
A VM running on a modern Type 1 hypervisor is very close to bare-metal performance, often within 5-10% of native speed. For most workloads, the difference is unnoticeable. The hypervisor is very efficient at translating VM instructions to real hardware.
Only on Apple hardware with Apple's own hypervisor framework. Most hypervisors (VMware, VirtualBox) do not support running macOS as a guest on non-Apple hardware due to Apple's licensing restrictions. This is not something the A+ exam tests in depth.
Multi-tenancy means that multiple customers (tenants) are sharing the same physical cloud infrastructure, but their data and workloads are logically isolated (like separate apartments in the same building). It is the fundamental model of public cloud computing that enables cost efficiency through resource pooling.
You've just covered Virtualization and Cloud Computing — now see how well it sticks with free 220-1201 practice questions. Full explanations included, no account needed.
Done with this chapter?