CompTIA A+: Virtualization and Cloud Computing Concepts
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Overview
This chapter explains how one physical computer can run many virtual computers, and how companies rent computing from cloud providers. It is the smallest part of Core 1, but the terms come up often in real help desk work.
A hypervisor is the software that runs virtual machines (VMs). A Type 1 hypervisor runs directly on the hardware and is used in data centers. A Type 2 hypervisor runs as an app on top of a normal operating system and is handy for testing on a desktop. VMs need enough CPU, memory, and storage on the host, and the CPU's virtualization support must be turned on in firmware. Containers are lighter: they share the host's operating system kernel and package only an app and what it needs.
Cloud services come in three main models. In Infrastructure as a Service (IaaS) you rent virtual servers and storage and manage the operating system yourself. In Platform as a Service (PaaS) you get a ready platform to run your own code. In Software as a Service (SaaS) you simply use finished software over the internet. Clouds can be public, private, hybrid (a mix), or community (shared by groups with the same needs). Key cloud features include rapid elasticity, which adds or removes resources as demand changes, and metered use, where you pay for what you use.
Key concepts
Type 1 hypervisor
Runs directly on the physical hardware (bare metal) with no general-purpose operating system underneath.
Memory tipData center servers = Type 1.
Type 2 hypervisor
Runs as an application on top of a normal operating system such as Windows or macOS.
Memory tipTesting an OS on your desktop = Type 2.
Container
A lightweight package that holds an app and its files and shares the host's operating system kernel instead of running a full guest OS.
Memory tipVM = whole computer. Container = just the app.
IaaS / PaaS / SaaS
IaaS rents servers, storage, and networks. PaaS gives a platform to build and run your own apps. SaaS delivers finished software you just use.
Memory tipYou manage the most in IaaS and the least in SaaS.
Rapid elasticity
The cloud adds resources when demand rises and removes them when demand falls, often automatically.
Memory tipBusy holiday sales = scale out; quiet month = scale in.
VDI
Virtual desktop infrastructure: user desktops run as VMs on central servers and users connect to them over the network.
Memory tipDesktop lives in the data center, not on the laptop.
Often tested
- A VM will not start on a new PC if hardware virtualization is turned off in firmware.
- Hybrid cloud mixes a private cloud or on-site systems with a public cloud.
- Web email and online office apps are examples of SaaS.
- A sandbox VM is a safe place to test updates or suspicious files without risking the real system.
Easy to confuse: Cloud service models
| Model | You get | You still manage |
|---|---|---|
| IaaS | Virtual servers, storage, network | Operating system, apps, data |
| PaaS | A ready platform to run code | Your apps and data |
| SaaS | Finished software | Your data and user accounts |
3 sample questions
Verified practice questions from this unit.
Question 1. Which type of hypervisor runs directly on the computer hardware without a general-purpose operating system underneath?
- ① Type 1 hypervisor
- ② Type 2 hypervisor
- ③ Container runtime
- ④ Web browser
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Answer: ① Type 1 hypervisor
Key point: Type 1 = bare metal; Type 2 = on top of an OS
A Type 1 hypervisor, also called a bare-metal hypervisor, is installed directly on the hardware. It is common on servers in data centers because it has less overhead. A Type 2 hypervisor runs inside a normal operating system.
Wrong choices
- Type 2 hypervisor: A Type 2 hypervisor runs as an app on top of an operating system such as Windows or macOS.
- Container runtime: A container runtime runs containers that share the host operating system. It still needs that operating system.
- Web browser: A web browser is an application. It does not run virtual machines on bare hardware.
Question 2. A company uses web-based email and office apps. Employees just sign in through a browser, and the provider manages the servers and the software. Which cloud service model is this?
- ① IaaS
- ② Type 1 hypervisor
- ③ SaaS
- ④ PaaS
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Answer: ③ SaaS
Key point: SaaS = finished software over the internet
Software as a Service (SaaS) delivers ready-to-use software over the internet. The provider runs everything behind it, and the customer simply signs in and uses it. Web email and online office apps are common examples.
Wrong choices
- IaaS: IaaS rents virtual servers and storage, and the customer manages the operating system and apps.
- Type 1 hypervisor: A hypervisor runs virtual machines. It is not a cloud service model.
- PaaS: PaaS gives developers a platform to build and run their own apps. Here the company uses finished apps.
Question 3. A technician wants to try a new operating system on a Windows desktop without changing or removing the installed Windows system. What is the best approach?
- ① Run the new operating system in a virtual machine using a Type 2 hypervisor
- ② Set up dual boot by changing the drive's partitions
- ③ Format the drive and install the new operating system
- ④ Set up RAID 1 with a second drive
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Answer: ① Run the new operating system in a virtual machine using a Type 2 hypervisor
Key point: Test an OS safely in a VM
A Type 2 hypervisor runs as an app on the existing Windows desktop. Inside it, the technician can create a virtual machine and install the new operating system there. The real Windows installation stays untouched, and the VM can be deleted when testing is done.
Wrong choices
- Set up dual boot by changing the drive's partitions: Dual boot changes the partitions on the drive and the boot setup, which can risk the existing system.
- Format the drive and install the new operating system: Formatting erases the existing Windows installation.
- Set up RAID 1 with a second drive: RAID 1 copies data between drives. It does not let you run a second operating system.
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