What are Virtual Machines?
Virtualization is a process that allows for more efficient utilization of physical computer hardware by using software to create an abstraction layer of computer hardware that allows hardware elements to be divided into multiple “virtual machines” (VMs). Each VM runs its own operating system and behaves like an independent computer, even though it is only running on a portion of the underlying computer hardware. Virtual desktop infrastructure (VDI) is enabled through hosting a desktop operating system within VMs that all run on a host server, which allows IT managers to deploy corporate data, applications, and desktops in a virtual data center and delivers them as a service via the internet. 1
A VM is a virtual environment that works like a computer within a computer. It runs on an isolated partition of its host computer and has its own CPU resources, memory resources, and operating system (e.g. Windows, Linux, macOS) resources. 2 This allows end-users to run applications on VMs and use them as they normally would on their workstations. Virtualization technology uses software to simulate virtual hardware that allows multiple VMs to run on a single machine. The physical machine is known as the host and the VMs running on it are referred to as guests. The process is managed by software known as a hypervisor. The hypervisor is a thin software layer responsible for managing and provisioning resources such as memory and storage from the host to the guests. It is also responsible for scheduling operations in VMs so that they do not overlap each other and put strain on the resources. VMs are only able to work when there is a hypervisor to virtualize and distribute host resources. There are two types of hypervisors:
Type 1 hypervisor. Type 1 hypervisors are also known as bare metal hypervisors. Type 1 hypervisors are installed natively on the underlying physical hardware. VMs interact directly with hosts to allocate hardware resources without any extra layers of software in between. Host machines that run type 1 hypervisors are only used for virtualization and they are often found in server-based environments like enterprise data centers. Some examples of type 1 hypervisors include Citrix Hypervisor, VMware, vSphere, and Microsoft Hyper-V.
Type 2 hypervisor. Type 2 hypervisors are also known as hosted hypervisors, and they run on the host computer’s operating system. Type 2 hypervisors pass VM requests to the host operating system which then distributes the appropriate physical resources to each guest. Type 2 hypervisors are slower than type 1 hypervisors because every action has to go through the host operating system first. Type 2 hypervisors are suitable for personal users or small businesses without dedicated servers for virtualization since their guest operating systems are not tied to physical hardware.
Benefits of VMs include:
Cost savings. VMs allow an organization to reallocate money spent on extra servers, when they can, instead, deploy multiple VMs for a fraction of the cost.
Increased scalability. Adding VMs is as simple as cloning copies of existing VMs in the physical machine.
Security. VMs enhance security by housing information on the host server rather than on personal devices. A compromised VM can be reverted to an older version or deleted and quickly recreated.
1 Shamir, 2021, “What is Virtual Desktop Infrastructure (VDI)?”
2 Citrix, 2021, “VDI and DaaS”