What is virtualization?

Host device

The physical server hardware that provides CPU, RAM, storage, and network interfaces across multiple VMs.

Virtual machine (VM)

VMs are software-defined devices hosting applications. Each VM runs its own guest operating system (OS) that interacts with the hypervisor.

Hypervisor

A hypervisor fills the gap between a device's hardware and the guest OS. It is usually a software, hardware, or firmware system that sits between the OS and the hardware. It allocates system resources like CPU, memory, and disk space from the physical server to the virtualized devices.

Hypervisors are also known as virtual machine monitors (VMMs). Based on the way they are deployed, hypervisors can be classified into two:

• Type 1: These are known as native or bare metal hypervisors. They are deployed directly on top of the server hardware.
• Type 2: They are known as hosted hypervisors. They are deployed as software applications running on top of a host-device OS.

Full virtualization

In this type of virtualization, the hypervisor takes the host resources, partitions them, and presents it to the VMs. The VMs are isolated from the host hardware. They are unmodified and unaware of their status as virtual devices. Hypervisors use a technology known as binary translation to allocate resources between the VMs and the host hardware. This is more secure and portable and can be implemented on any OS. But as binary translation is used, it is slower.

Para virtualization

The VMs are not completely isolated from the host server. The VMs take care of resource allocation themselves. The VMs are modified and aware of themselves. They communicate with both the hypervisor and the host system. Para virtualization is faster but less portable. Moreover, as the guest OSs are modified, the number of OSs on which this can be implemented is limited.

Hardware-assisted virtualization

This approach combines the speed of para virtualization with the flexibility of full virtualization with hardware extensions. Instead of using binary translation, extensions like Intel VT-x or AMD-V intercepts communications between the VMs and the hardware. This allows a greater range of unmodified OSs to run at near native hardware speed.

OS virtualization

The OS acts as a hypervisor and creates virtual spaces within the system that are independent of each other. The OS partitions the system resources into isolated instances. These isolated virtual spaces are also called containers. They are faster to boot, however, they share the same host kernel. A kernel-level exploit could compromise the entire cluster. Moreover, you cannot run different OSs like Windows and Linux within the same host.

Kernel-level virtualization

The OS's own kernel is converted into a bare-metal hypervisor. They are generally implemented on Linux kernel modules like KVM (Kernel-based virtual machine).

1. Server virtualization

Server virtualization is the process of dividing one physical server into multiple isolated VMs. It allows organizations to maximize hardware utilization by running multiple workloads simultaneously instead of dedicating one server per application. This significantly reduces infrastructure costs and energy consumption.

It forms the foundation of modern data centers by enabling rapid provisioning, workload mobility, and high availability without requiring additional physical hardware.

2. Desktop virtualization

Desktop virtualization separates a user’s desktop environment from their physical device. It enables secure access to corporate desktops from any location or device, supporting remote work strategies and reducing dependency on physical office infrastructure.

Centralized desktop management allows IT teams to apply updates, enforce policies, and maintain compliance across thousands of endpoints from a single console.

3. Storage virtualization

Storage virtualization combines multiple physical storage systems into a unified logical pool. Storage pools and LUNs work on the basis of this. A storage area network (SAN) is a dedicated network that connects storage devices. A SAN is not connected to a LAN but has its own set of SAN switches to connect storage arrays.

A redundant array of independent disks (RAID) is a storage virtualization technology where disks are combined to form a virtual storage unit. Multiple levels of RAIDs are available with varying levels of speed, capacity, fault tolerance, and reliability.

Centralized storage control simplifies backup, replication, and disaster recovery processes while allowing seamless expansion without downtime.

4. Network virtualization

Network virtualization creates software-defined networks independent of physical hardware. Administrators can configure routing, segmentation, and security policies programmatically, reducing manual configuration and deployment time.Software defined networking and virtual LANs are applications of this.

It enables advanced architectures such as micro-segmentation and automated traffic optimization, improving performance, and strengthening security.

5. Application virtualization

Application virtualization isolates software from the underlying operating system. Applications run in self-contained environments, preventing compatibility conflicts and eliminating the need for traditional installation on individual machines.

Updates and patches can be deployed centrally, ensuring users always access the latest version without disrupting workflows.

6. Unified computing systems

A unified computing system (UCS) is a converged data center architecture that combines server virtualization, with network fabrics and storage networks. A UCS usually has a powered chassis with a cooling unit and slots to connect blade servers and rack servers. Virtual hosts can be connected to the server slots and interconnected with a virtualized network. A UCS can be connected to a SAN to provide virtualized storage capabilities.

7. Hyper-converged infrastructure (HCI)

HCI virtualizes networking, servers, and storage systems into a set of underlying physical devices. Administrators can manage compute, routing, and storage from a single environment. Unlike UCS, HCI is a software-defined framework. Modern HCI platforms like Nutanix can be hosted in Cisco UCS hardware.

1. Server consolidation

A company running 50 physical servers for separate apps can reduce them to 5 high-capacity hosts using virtualization. This improves resource utilization while simplifying infrastructure management and monitoring.

2. Development & testing labs

Engineering teams create temporary virtual environments to test software, simulate failures, or validate updates. These environments can be deployed instantly and deleted after use. This accelerates release cycles and minimizes infrastructure waste.

3. Disaster recovery systems

Enterprises replicate VMs to backup locations so workloads can be restored quickly after outages or cyber incidents. Recovery time drops from hours or days to minutes, helping organizations meet uptime SLAs and avoid revenue loss.

4. Secure sandboxing

Security teams run suspicious files or applications inside isolated VMs to analyze their behavior. Even if malwares execute, they remains contained within the virtual environment.

5. Containerization

Containerization builds on virtualization concepts but operates at the operating-system level rather than emulating full hardware. VMs virtualize hardware to run multiple OS environments, whereas containers share a single kernel while isolating applications.

Platforms like Docker and orchestration systems such as Kubernetes rely on virtualization infrastructure underneath to scale efficiently across hosts.

6. Cloud computing

Virtualization is the foundational technology enabling cloud computing. Cloud providers use virtualization to divide physical servers into isolated environments.This abstraction makes it possible to deliver on-demand compute, storage, and networking resources without requiring dedicated hardware for each user.

7. Workspace virtualization

Workspace virtualization separates a user’s desktop and applications from the physical device, delivering them as a managed service. Users can access their desktops from any location, device, or platform.

8. VM migration

VM migration enables running workloads to move between hosts, storage systems, or data centers without downtime. This ensures continuous availability, automated load balancing, and improved disaster recovery resilience.