What Is a Virtual Machine? Definition & Guide

What is a virtual machine? definition & guide 

A virtual machine, or VM, is a software-defined computer that exists only as code within a physical server. It is a digital version of a physical computer and works just like a computer within a computer. 

The virtual environment runs on an isolated partition of the host computer and has its own operating system, CPU power, memory, disks for file storage, ability to connect to the internet, and other necessary resources. 

Virtualisation is the process of creating a virtual version of a computer that functions like a physical computer. A virtual machine uses software to run programs and deploy apps instead of a physical computer. 

Virtual guest machines operate within a physical host machine. This can be useful both in the cloud and across on-premises environments. 

Using VMs can be more cost-effective, provide resources to multiple users at the same time and in different locations, be more efficient, and offer increased flexibility.

What are virtual machines?

A software-based digital computing system, a virtual machine (VM) can perform all of the functions of a physical computer. 

VMs use the resources of a physical “host” computer and/or a remote server to run as a virtual “guest.” This digital version of a physical computer, the virtual machine, is a computer file called an image that acts like a regular computer. The VM will borrow a set amount of CPU, storage, and memory from its physical host and run in an isolated partition separate from the host.

The virtual machine can function as a replacement for a physical computer, or it can run as a separate computing environment in a separate window, often to allow for the use of an alternative operating system to the host. Virtual machines do not interfere with the host computer’s operating system and therefore can often be used for software or application testing. 

Virtual machines are often deployed to allow for remote use and have enabled cloud computing to take off.

How virtual machines work

Virtual machines use virtualisation technology, which works to create a virtual, software-based computer. Resources are provisioned from the host to the guest — a process that is managed by software called a hypervisor. The hypervisor ensures that operations are scheduled so the host and the guest (physical computer and virtual machine) can work in tandem without disrupting each other. 

Virtual machines can exist on a physical computer host or a remote server, such as one in a cloud provider’s data centre, for example. These VMs function the same as an actual computer and commonly run in an application window or on the operating system of a physical machine. 

Types of virtual machines

There are two main types of virtual machines: process VMs and system VMs. 

A process VM provides a platform-independent programming environment. The process virtual machine allows a single process to run as an application on the host machine while ignoring information on the underlying operating system or hardware. This can allow a machine to run an application on a host machine that the operating system typically does not support.

A system VM is a complete substitution of a physical machine, and it is fully virtualised. A host computer’s physical resources can be shared between various virtual machines, each of which is running its own copy of the operating system on the system platform. The hypervisor runs on top of the operating system or on bare hardware to complete the virtualisation process.

5 types of virtualisation

The components that make up an IT infrastructure or that make up a traditional data centre can be virtualised. Here are five specific types of virtualisation:

1. Network virtualisation: Companies with a high volume of users who need constant access to a network can benefit from network virtualisation. This type of virtualisation allows multiple sub-networks to be created on the same physical network. The equipment is combined into one software-based virtual network.

   Bandwidth can also be divided into multiple independent channels that are assigned individually to servers and devices. Network virtualisation can increase network speed, reliability, and security, and it can allow for improved monitoring of data usage.

2. Hardware virtualisation: Also known as server virtualisation, hardware virtualisation creates virtual versions of operating systems and computers and consolidates them into one primary physical server. The virtual machines are managed by a hypervisor that communicates with the physical CPU and server’s disk space. 

   With hardware virtualisation, multiple operating systems can be run on one machine, and hardware resources are used more efficiently.

3. Software virtualisation: A computer system complete with hardware is created with software virtualisation to allow a guest operating system (or more than one) to run on a physical host machine using the same hardware.

   Applications are also able to be virtualised and then delivered from a server to an end user’s device. Software virtualisation allows remote users to access centrally hosted applications.

4. Desktop virtualisation: With desktop virtualisation, the desktop environment is separated from the physical device and stored on a remote server. Users are then able to access their desktop on any device from any location.

   This allows for ease of management, cost savings on software licenses and updates, better data security, and enhanced accessibility.

5. Storage virtualisation: Using storage virtualisation, multiple physical storage devices can be consolidated to appear as one single device. This can allow for quick and easy duplication to transfer virtual storage data to another location in the event of a disaster or crisis.

   Storage virtualisation can reduce costs, increase speed and performance, and improve load balancing.

Who uses virtual machines?

Virtual machines are commonly used by entities supporting remote or hybrid workplaces by enabling employees to complete their work from anywhere. The virtual machine allows employees to access their desktop and centrally hosted applications from alternate locations the same way as if they were on-premises. 

Public cloud services use VMs as well. They commonly allow multiple users to use virtual application resources at the same time.

Virtual machines can be used by developers and testers to build and deploy apps to the cloud, test software or a new (or beta release) operating system, and run dev-test scenarios. Virtual machines can also allow individuals who need to run apps or software on operating systems they were not meant for to do so. 

A VM can run an old application that is no longer supported by a new operating system or allow a user to access virus-infected data. Virtual machines can also serve as a tool for backing up your existing operating system.

Benefits of virtual machines

Virtual machines run their own operating systems and applications, much like a physical computer, but they have the distinct advantage of remaining independent of the host and other VMs sharing the same host. Here are some of the additional benefits of virtual machines:

• Cost-effectiveness: Using virtual machines can lower your hardware and infrastructure costs, as you are basically able to use one machine to run multiple. You will not need to run as many servers to accomplish the same goals, for example. Physical hardware is leveraged at a higher capacity, providing the same outcome with a much lower price tag.

• Flexibility: A virtual machine allows for more than one operating system to run on the same machine. This can be especially helpful if you want to run a Linux virtual machine on a Windows operating system, for example.

  It can allow you to run applications that are supported by different operating systems than the host is running. The need can also arise to run an older version of an operating system, which can also be done with a VM.

• Scalability: Apps are more easily scaled using VMs, as you can simply create a new VM on the existing physical machine to accommodate load fluctuations to stabilise performance. This is a much faster and easier process than needing to install different operating systems on physical servers.
• Speed, agility, and simplicity: VMs are easy and quick to set up. They are much simpler than provisioning a new testing environment for developers. The process of running dev-test scenarios is much faster when using virtualisation.

• Security:  Apps of questionable security can be run on a VM without impacting or affecting the underlying hardware or the components of the host. Viruses can be isolated to avoid risk to the host computer and safely studied.

  This can make a VM ideal for testing software changes or new applications. If the VM is compromised, it can be easily deleted and recreated or restored to an older version — all without impacting the host’s operating system.

• Decreased downtime: A VM can be a great solution for a backup and use with disaster recovery, as it can easily be moved from one hypervisor to another if the host crashes or is unavailable. This can mean that the system will not be down for as long in the event of a crisis.
• More efficient performance: Using a virtual machine can increase the speed and performance of applications by provisioning resources more efficiently. VMs can also be beneficial for load balancing.
• Portability: Virtual machines can be created on host computers or machines and easily transported when necessary. As VMs run independently of one another, they are highly portable and allow for remote access and the ability to reach resources hosted elsewhere.

Additional resources

Microsoft provides Windows virtual machines as well as Linux virtual machines in Azure. Apple also offers information on how to install macOS on a virtual machine.

References

Virtual Machine. PC Mag.

Windows 11. (2022). Microsoft.

Windows Virtual Machines. (2022). Microsoft.

Linux Virtual Machines in Azure. (2022). Microsoft.

Installing macOS on a Virtual Machine. (2022). Apple, Inc.