What is virtualization?

This helps make better use of hardware, lower costs, and improve flexibility. Since each virtual machine is isolated, it also adds a layer of security and makes it easier to test, scale, and manage systems.

From individual developers testing software to large companies running many virtual servers in the cloud, virtualization is a foundation of modern IT infrastructure.

Virtualization and cloud computing are often linked, but they serve different purposes:

• Virtualization is the technology that divides one physical machine into multiple virtual environments or resource partitions.
• Cloud computing builds on this foundation to deliver those virtualized resources, such as servers, storage, and applications, over a network. It enables users, teams, or entire organizations to access a shared pool of resources that are automatically managed and scaled to demand.

Put simply, virtualization creates the virtual resources, while cloud computing provides a flexible system for delivering and managing them.

Virtualization is based on two key components: virtual machines and hypervisors.

Virtual machines (VMs)

A virtual machine is a software-based version of a computer that acts like a real one. It has its own CPU, memory, storage, and operating system, all created from a pool of physical resources. Because each VM is isolated, it can be moved between devices and will work the same way everywhere.

Virtualization makes it possible to run multiple operating systems at once on a single physical device. For example, you can run Windows or macOS on a Linux computer. Each system works as if it were running directly on the hardware, so the user experience stays the same.

Hypervisors

A hypervisor, also called a virtual machine monitor (VMM), is the software that manages virtualization. It separates the physical hardware and allocates resources (CPU, memory, and storage) to different virtual machines.

When a VM needs more resources, the hypervisor connects it to the physical system and handles the request almost instantly.

There are two main types of hypervisors:

• Type 1, bare-metal: Installed directly on the hardware. It manages VMs without needing a host operating system and is common in data centers and servers.
• Type 2, hosted: Runs on top of an existing operating system as an application. It's used mainly by individuals who want to run several operating systems on one computer.

HOW THE PIECES WORK TOGETHER

• The hypervisor boots and discovers available CPU, memory, storage, and network.
• An admin defines a VM, choosing its virtual CPU count, RAM size, virtual disk, and network.
• The hypervisor carves out those resources from the physical pool and presents them to the VM as virtual hardware.
• An operating system installs inside the VM and uses the virtual hardware as if it were physical.
• During runtime, the hypervisor maps VM requests to the real hardware, balances load across VMs, and enforces security and isolation.
• If a VM needs more or fewer resources, the hypervisor can adjust allocations, often without downtime.
• VMs can be snapshotted, migrated to another host, or restarted from images for high availability and recovery.

The three most common types of virtualization are server virtualization, desktop virtualization, and storage virtualization. Each helps make IT resources more flexible and efficient.

1. Server virtualization
This method divides one physical server into several VMs. Each VM runs its own operating system and applications, allowing multiple workloads to share the same hardware. This improves efficiency, reduces costs, and simplifies management.

2. Desktop virtualization
Desktop virtualization delivers desktop environments from a central server to multiple users or devices. Employees can access their personalized desktops from any location while administrators manage and update everything in one place. It increases security and makes maintenance easier.

3. Storage virtualization
This type combines several physical storage devices into one virtual storage pool. It gives users a single, unified view of all available storage, making data management simpler and improving flexibility, scalability, and access speed.

Virtualization helps organizations save money, improve flexibility, and scale faster, but it also brings new security and management challenges. Here's a quick overview:

• Cost efficiency: Reduces the number of physical servers, cutting hardware, energy, and maintenance costs while improving resource use.
• Speed and flexibility: New virtual machines can be created, moved, or removed in minutes, making provisioning and scaling much faster.
• High availability: Features like live migration allow maintenance without downtime, improving business continuity.
• Better testing and development: Multiple environments can run on one server, making it easy to test new systems or applications.
• Centralized management: Administrators can manage multiple systems from one place, simplifying operations.

• Resource contention and performance overhead: Because many VMs share the same hardware, performance can drop under heavy load. Fine-tuning resource allocation and monitoring latency becomes critical.
• Security exposure at the hypervisor layer: If the hypervisor is compromised, attackers can gain access to all virtual machines. Misconfigurations, weak isolation, or outdated software increase this risk.
• VM sprawl and resource waste: The ease of creating VMs often leads to uncontrolled growth. Dormant or forgotten instances still consume storage, licenses, and management time.
• Complex compliance and auditing: Tracking configurations, updates, and access controls across virtualized systems is harder than in physical environments, complicating compliance and audits.
• Management overhead and skill requirements: Virtualization demands skilled administrators who understand hypervisors, automation tools, and capacity planning. Without them, environments can quickly become unstable.
• Licensing and vendor lock-in: Different hypervisor vendors use inconsistent licensing rules, and switching platforms can be costly and time-consuming.