Virtual machine (VM)

Definition

A Virtual Machine (VM) is a software-based simulation of a physical computer system. It runs an independent operating system (OS) and applications while sharing the physical hardware resources of the host machine. VMs are managed by a hypervisor, which allocates CPU, memory, storage, and networking resources across multiple virtualized environments.

VMs provide isolation, meaning that applications running inside them are separated from the host and other VMs. This makes them ideal for running multiple workloads on a single server, testing software in different OS environments, or consolidating hardware in enterprise data centers.

Advanced

From a technical perspective, VMs rely on hypervisors (Type 1 bare-metal or Type 2 hosted) to abstract hardware and present virtualized devices to guest operating systems. Each VM includes a virtual disk, virtual CPU, memory allocation, and virtual network interface. Snapshots and cloning enable rapid recovery and duplication of environments.

In enterprise IT, VMs support workload mobility, disaster recovery, and hybrid cloud deployments. They integrate with orchestration platforms for automated scaling, balancing, and failover. While containers offer lighter-weight alternatives, VMs remain crucial for workloads that require full OS-level isolation, legacy application support, or compliance-driven segmentation.

Why it matters

• Increases hardware efficiency by consolidating multiple systems on one host.
• Provides strong workload isolation for security and stability.
• Supports testing, development, and cross-platform compatibility.
• Enables disaster recovery and business continuity planning.

Use cases

• Running legacy applications on modern hardware.
• Hosting multiple operating systems on a single server.
• Providing isolated test and development environments.
• Powering Infrastructure as a Service (IaaS) offerings.

Metrics

• VM density (number of VMs per host).
• Resource utilization (CPU, RAM, storage).
• Performance overhead compared to bare-metal systems.
• Uptime and recovery speed from snapshots.
• VM provisioning time and automation efficiency.

Issues

• Performance overhead compared to running directly on hardware.
• Security risks if hypervisors or guest OS are compromised.
• Resource contention when hosts are overloaded.
• Licensing costs and management complexity in large environments.

Example

A healthcare company runs its electronic medical record (EMR) system on virtual machines. This setup isolates sensitive applications, allows scaling without new hardware purchases, and provides snapshot-based recovery to meet regulatory compliance.