Virtual machines use virtualization technology to create virtual hardware—or a virtual version of a computer on a physical machine. The physical machine on which the VMs run is called the host, and the VMs running on the host are called guests. 

Each guest VM runs on an isolated partition on the host, completely separated from other guests. You can host multiple VMs on a single host machine, often a server, running on a software layer known as the hypervisor.

The hypervisor abstracts the host machine’s physical resources, such as compute, memory, or storage, into a pool that can be provisioned and dynamically allocated to guest VMs as needed, providing more flexibility and increasing overall efficiency.

Generally speaking, there are two types of virtual machines: process VMs and system VMs. 

• Process VM: A process VM, also called an application virtual machine or managed runtime environment (MRE), creates a virtual environment of an OS while an app or single process is running and destroys it as soon as you exit. Process VMs enable creating a platform-independent environment that lets an app or process run the same way on any platform.
• System VM: A system VM (sometimes called hardware virtual machines) simulates a complete operating system, allowing multiple OS environments to live on the same machine. Typically, this is the type of VM people are referring to when they talk about “virtual machines.” System VMs can run their own OS and applications, and a hypervisor monitors and distributes the physical host machine’s resources between system VMs. 

More recently, you may have also heard people discussing virtual machines in the cloud or a cloud VM. Cloud virtual machines are simply virtual machines that run on virtual servers in the cloud. Many cloud service providers let you create and run cloud virtual machines on their infrastructure, allowing you to use their powerful servers as host machines and leverage other software-defined services such as memory and network storage. 

Watch the video episode of VM End to End below to learn more about what a virtual machine is in cloud computing and what your business can do with a cloud VM. 

There are, however, some considerations to keep in mind when running VMs. One of the biggest potential challenges of virtual machines is that running multiple operating systems and a hypervisor layer can come with a performance cost if the host machine isn’t robust enough. In addition, virtual hardware may not be as efficient as the physical hardware of a physical machine. 

Many of these concerns though can be overcome by choosing to use VMs offered by a cloud service provider. Cloud VMs provide many advantages over traditional VMs since they offer organizations access to the computing power of an entire data center’s worth of computers, rather than a single machine. 

For example, Google Cloud virtual machines sizes can expand to include higher CPU and memory. It also optimizes its machine types around specific customer needs for compute-intensive workloads, high memory configurations, or demanding workloads like machine learning or high performance computing. 

Google Cloud even offers shielded virtual machines for extra security and verifiable integrity of your VM instances. Google Cloud shielded virtual machines leverage advanced platform security capabilities and controls that protect enterprise workloads from threats like remote attacks, privilege escalation, and malicious insiders. 

VMs are the basic building blocks of virtualized computing resources and play a primary role in creating any application, tool, or environment—both in the cloud or on-premises. 

Here are a few of the more common ways businesses use virtual machines:

• Consolidate servers: Multiple physical machines can be reconfigured as a VM and run on a host alongside other VMs, allowing organizations to reduce sprawl.
• Create development and test environments: VMs can serve as isolated environments for testing and development that include full functionality but have no impact on the surrounding infrastructure.
• Support DevOps: VMs can easily be turned off or on, migrated, and adapted, providing maximum flexibility for development. 
• Enable workload migration: The flexibility and portability that VMs provide are key to increasing the velocity of migration initiatives.
• Improve disaster recovery and business continuity: Replicating systems in cloud environments using VMs can provide an extra layer of security and certainty. Cloud environments can also be continuously updated.
• Create a hybrid environment: VMs provide the foundation for creating a cloud environment alongside an on-premises one, bringing flexibility without abandoning legacy systems.

Compute Engine is Google Cloud’s flexible virtual machine offering, allowing you to create and run virtual machines in predefined or custom machine sizes on Google’s infrastructure. Compute Engine provides all the tools you need to help you accelerate your digital transformation and bring your existing applications to the cloud. 

With Compute Engine, you can validate, run, and migrate your systems without having to rewrite your applications, modify images, or change your management processes. 

Need help choosing the right VM for your workload? Explore the VM selection tool to get our recommendations.