---
title: What is server virtualization?
url: https://www.vmware.com/topics/server-virtualization
description: Learn about server virtualization, which divides a physical server into multiple virtual servers through a software application.
---

# What is server virtualization?

Server virtualization is the process of dividing a physical server into multiple unique and isolated virtual servers by means of a software application. Each virtual server can run its own operating system independently. This technology masks server resources from server users, including the number and identity of operating systems, processors, and individual physical servers.

## Why server virtualization

Server virtualization is a cost-effective way to utilize existing resources in IT infrastructure. It solves the following problems:

- **Resource underutilization:** Without server virtualization, servers only use a small part of their processing power. This results in servers sitting idle because the workload is distributed to only a portion of the network’s servers.
- **Data center overcrowding:** Physical infrastructure becomes overcrowded with underutilized servers, causing a waste of resources and power. This inefficiency leads to higher operational costs and a negative environmental impact.
- **Cost inefficiency:** Organizations face significant capital and operational expenses in maintaining numerous physical servers that operate below capacity.

By using this technology and dividing each physical server into multiple virtual servers, server virtualization allows each virtual server to act as a unique physical device. Each virtual server can run its own applications and operating system, dramatically increasing the utilization of resources and the capacity of each physical machine. The different forms of server utilization further solve these challenges in their own way (described below).

## How server virtualization works

Server virtualization abstracts network, storage, and compute resources so applications, services, and functions become less dependent on physical hardware. IT administrators can provide applications and services with their own environment, including an operating system, support software, network, and storage resources, that is less prone to problems caused by other workloads running on the same underlying resources.

### Hypervisors in server virtualization

At the heart of most virtualization implementations is the [hypervisor](https://www.vmware.com/topics/hypervisor) (also called a Virtual Machine Monitor, or VMM), which serves as the key component that creates and manages multiple virtual machines on a single physical host. The hypervisor forms a layer between the hardware and the operating systems, performing critical functions. 

Hypervisors:

- Identify and handle privileged CPU instructions,
- Manage memory allocation,
- Schedule processes across virtual machines (VM), and
- Provide virtualized hardware resources to each [VM](https://www.vmware.com/topics/virtual-machine).

VMs can either share resources to reduce costs and improve overall utilization and performance, or they can be provided with dedicated resources when needed. Problems identified in any single workload are isolated from other workloads, ensuring stability across the virtualized environment.

## Types of server virtualization

Server virtualization can be implemented through five primary approaches, each offering different levels of abstraction, performance characteristics, and hardware dependencies. Each approach addresses specific use cases and organizational requirements around performance, compatibility, cost, and management complexity.

### Full Virtualization

Full virtualization provides complete hardware emulation, allowing unmodified guest operating systems to run as if they were on real hardware. The hypervisor intercepts (traps) hardware instructions from the guest OS and emulates them in software.

This is how this type of virtualization works: The virtualization layer creates a complete simulation of the underlying hardware. Every instruction from the guest OS passes through the hypervisor, which translates it for the physical hardware. This approach requires no modifications to the guest operating system.

One example of full virtualization would be the VMware ESX Server.

### Para-Virtualization

Para-virtualization focuses on improving performance by reducing emulation overhead. The guest operating system is modified and recompiled before installation to communicate directly with the hypervisor.

This is how this type of virtualization works: Rather than emulating hardware, para-virtualization creates isolated domains where each workload operates independently. The guest OS is aware of the virtualization layer and optimizes privileged calls and system interactions accordingly. The network works together as a cohesive unit, with each virtual server aware of others in the environment.

Some noteworthy examples of para-virtualization include Xen (which supports both full virtualization and para-virtualization, using modified Linux Domain 0 as the administrative OS), and Oracle VM for x86.

### Hardware-Assisted Virtualization

Hardware-assisted virtualization enhances full virtualization by using processor-level extensions to reduce the hypervisor’s workload. Modern CPUs include built-in support that allows the hardware itself to manage privileged operations and I/O requests efficiently.

This is how this type of virtualization works: The OS and software do the heavy lifting, but call upon hardware capabilities to provide optimized virtualization with minimal performance loss. CPU extensions handle privileged instructions directly, and APIs pass calls from the application layer down to the hardware, bypassing emulation overhead.

Some noteworthy examples of hardware-assisted virtualization include Intel VT (Virtualization Technology / Vanderpool) and AMD-V (Virtualization / Pacifica).

### Hypervisor-Based Virtualization

Hypervisor-based virtualization is the most common form of virtualization in organizations’ data centers. The hypervisor (Virtual Machine Monitor) creates and manages multiple virtual machines on a single physical host, serving as the critical abstraction layer.

This is how this type of virtualization works: The hypervisor identifies and handles privileged CPU instructions, manages memory, schedules processes, and provides virtualized hardware resources to each VM. It sits between the hardware and virtual machines, orchestrating resource allocation and ensuring isolation.

### OS-Level Virtualization (Containerization)

OS-level virtualization, also known as containerization or system-level virtualization, allows multiple isolated user-space environments (containers) to run on a single OS kernel. Instead of running separate kernels, all containers share the same host OS kernel.

This is how this type of virtualization works: Based on the chroot mechanism, each [container](https://www.vmware.com/topics/containers) has its own root directory and process space but shares the same kernel. Different workloads share underlying resources in a mutually distrusting manner; problems caused by one workload shouldn’t create problems for others. This creates extremely lightweight virtualization compared to full virtual machines.

Some noteworthy OS-level virtualization examples include Docker and Linux Containers (LXC).

## Server virtualization benefits

There are many benefits to leveraging server virtualization, including:

- **Maximized server capacity:** Server virtualization dramatically increases hardware utilization by allowing multiple virtual servers to run on a single physical machine.
- **Reduced physical infrastructure:** By consolidating multiple virtual servers onto fewer physical machines, organizations can significantly reduce their data center footprint. This “higher server ability” means fewer physical servers are needed to support the same or greater workload, freeing up valuable rack space and reducing facility requirements.
- **Lower operating costs:** Virtualization delivers cost savings across multiple dimensions:
  - Lower hardware acquisition costs (fewer physical servers needed)
  - Reduced power consumption (fewer machines running)
  - Decreased cooling requirements (less heat generation)
  - Lower maintenance expenses (fewer physical components to manage)
  - Reduced software licensing costs through better utilization
- **Simplified administration:** Virtualization eliminates server complexity through centralized management platforms.  
  IT administrators can:
  - Provision new servers in minutes instead of days
  - Deploy workloads more quickly without hardware procurement delays
  - Manage entire virtual infrastructure from a single console
  - Standardize configurations and enforce policies automatically
- **Increased application performance:** Virtual machines can be right-sized to application needs and dynamically adjusted as requirements change, ensuring optimal performance without over-provisioning.
- **Enhanced flexibility and agility:** Organizations can respond faster to business demands by rapidly deploying new services or scaling existing ones without waiting for hardware procurement.
- [Improved disaster recovery:](https://www.vmware.com/topics/disaster-recovery): Virtual machines are files that can be easily backed up, replicated, and restored, dramatically improving business continuity capabilities.
- **Better testing and development:** Developers can quickly spin up isolated environments for testing without impacting production systems or requiring dedicated hardware.
- **Workload mobility:** Virtual machines can be moved between physical hosts (live migration) for load balancing, maintenance, or hardware upgrades without service interruption.

## Recommended for You

## How VMware products can help

[VMware vSphere](https://www.vmware.com/products/cloud-infrastructure/vsphere) provides an enterprise-grade platform that helps keep pace with technological innovation, supporting modern and traditional workloads.

vSphere helps extract maximum performance from workloads by enabling easier management of underlying infrastructure, dynamically load-balancing workloads, and freeing up CPUs to do more by offloading infrastructure functions.

Our solution provides the best intrinsically secure platform to enforce security across the entire infrastructure stack.

## Recommended for You

- [Virtual Machine (VM)](https://www.vmware.com/topics/virtual-machine)
- [Hypervisor](https://www.vmware.com/topics/hypervisor)
- [Private Cloud](https://www.vmware.com/topics/private-cloud)
- [Data Center](https://www.vmware.com/topics/data-center)

## Related Products and Solutions

- [VMware vSphere](https://www.vmware.com/products/cloud-infrastructure/vsphere)
- [VMware Cloud Foundation](https://www.vmware.com/products/cloud-infrastructure/vmware-cloud-foundation)
- [VMware vSphere Foundation](https://www.vmware.com/products/cloud-infrastructure/vsphere-foundation)

## Also of Interest

- [What is Platform Engineering?](https://www.vmware.com/topics/platform-engineering)
- [What is a Virtual Machine?](https://www.vmware.com/topics/virtual-machine)
- [What is Virtual Infrastructure?](https://www.vmware.com/topics/virtual-infrastructure)