TL;DR
A virtual machine (VM) is a software-based computing environment that runs on a physical host machine, sharing its resources through a layer of software called a hypervisor. VMs come in two core types — process and system — and support five forms of virtualization: network, hardware, software, desktop, and storage. They are widely used by remote workforces, developers, cloud providers, and testers because they deliver cost savings, flexibility, scalability, security isolation, and faster disaster recovery compared to traditional physical infrastructure.
What are virtual machines?
A 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, central processing unit (CPU) power, memory, disks for file storage, ability to connect to the internet, and other necessary resources.
Virtualization 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.
How does a VM relate to its host machine?
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
- More capable of serving multiple users simultaneously across locations
- More efficient
- More flexible
A software-based digital computing system, a 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 do virtual machines work?
Virtual machines use virtualization technology, which works to create a virtual, software-based computer.
What role does the hypervisor play?
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.
Where can virtual machines be hosted?
Virtual machines can exist on a physical computer host or a remote server, such as one in a cloud provider's data center, 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.
What are the types of virtual machines?
There are two main types of virtual machines: process VMs and system VMs.
| Type | Description | Key characteristic |
|---|---|---|
| Process virtual machine (VM) | Provides a platform-independent programming environment | Allows a single process to run as an application, ignoring the underlying OS or hardware |
| System virtual machine (VM) | A complete substitution of a physical machine; fully virtualized | Shares a host's physical resources across multiple VMs, each running its own OS |
5 types of virtualization
The components that make up an information technology (IT) infrastructure or that make up a traditional data center can be virtualized. Here are five specific types of virtualization:
Network virtualization: Companies with a high volume of users who need constant access to a network can benefit from network virtualization. This type of virtualization 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 virtualization can increase network speed, reliability, and security, and it can allow for improved monitoring of data usage.
Hardware virtualization: Also known as server virtualization, hardware virtualization 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 virtualization, multiple operating systems can be run on one machine, and hardware resources are used more efficiently.
Software virtualization: A computer system complete with hardware is created with software virtualization 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 virtualized and then delivered from a server to an end user's device. Software virtualization allows remote users to access centrally hosted applications.
Desktop virtualization: With desktop virtualization, 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.
Storage virtualization: Using storage virtualization, 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 virtualization can reduce costs, increase speed and performance, and improve load balancing.
Who uses virtual machines?
Virtual machines are used across a wide range of industries and roles. The following groups represent some of the most common users.
How do remote and hybrid workplaces use 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.
How do public cloud services use virtual machines?
Public cloud services use VMs as well. They commonly allow multiple users to use virtual application resources at the same time.
How do developers and testers use virtual machines?
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.
How do virtual machines support legacy applications?
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.
What are the 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:
How do virtual machines reduce hardware costs?
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.
How do virtual machines provide operating system 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.
How do virtual machines support 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 stabilize performance. This is a much faster and easier process than needing to install different operating systems on physical servers.
How do virtual machines improve speed and agility?
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 virtualization.
How do virtual machines enhance 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.
How do virtual machines help decrease 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.
How do virtual machines improve performance efficiency?
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.
How portable are virtual machines?
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.
Frequently asked questions
What is the difference between a process virtual machine (VM) and a system virtual machine (VM)?
A process VM provides a platform-independent environment for running a single application, allowing it to operate regardless of the underlying operating system or hardware. A system VM, by contrast, is a fully virtualized substitute for an entire physical machine, capable of running its own complete operating system and sharing the host's physical resources with other VMs.
What is a hypervisor and why does it matter?
A hypervisor is the software layer that manages the allocation of resources — such as CPU, memory, and storage — from a physical host machine to its virtual machines. It ensures that the host and guest systems can operate simultaneously without interfering with each other.
How do virtual machines (VMs) improve security?
Because VMs run in isolated partitions separate from the host operating system, potentially harmful applications or virus-infected data can be contained within the VM. If a VM is compromised, it can be deleted and recreated or rolled back to a previous state without affecting the host or other VMs on the same machine.
Can a virtual machine (VMs) run a different operating system than the host?
Yes. One of the key advantages of VMs is their flexibility — they can run operating systems that differ from the host. For example, a Linux VM can run on a Windows host machine, and older operating system versions can also be run on modern hardware through virtualization.
What happens to a virtual machine (VM) if the host server crashes?
A VM can be moved from one hypervisor to another if the host crashes or becomes unavailable, which significantly reduces downtime. This portability makes VMs a practical tool for backup strategies and disaster recovery planning.
What types of organizations benefit most from virtual machines (VMs)?
Organizations supporting remote or hybrid workforces, public cloud service providers, software development and testing teams, and businesses running legacy applications all benefit from VMs. They are also useful for any entity looking to reduce hardware costs, improve scalability, or increase the efficiency of their IT infrastructure.
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.
