What are the Basic Concepts of Virtualization

 Basics Concepts and Implementation levels of  Virtualization

Basic Concepts of Virtualization

1. Virtualization: Introduction

Virtualization is a fundamental concept in modern computing that allows multiple virtual instances to run on a single physical machine. It involves the abstraction and isolation of resources, such as processors, memory, storage, and networking, to create virtual environments that behave as independent systems. Virtualization enables improved resource utilization, flexibility, and scalability in various computing environments. Let's explore the basic concepts of virtualization:

1.a Hypervisor / Virtual Machine Monitor (VMM):

At the core of virtualization is a software layer called the hypervisor or Virtual Machine Monitor (VMM). The hypervisor acts as a mediator between the physical hardware and the virtual environments running on it. It manages and allocates resources, provides isolation, and facilitates communication between virtual machines (VMs) and the underlying hardware.There are two types of hypervisors:

A host operating system is not necessary for Type 1 hypervisors, which run directly on the physical hardware. They offer higher performance and efficiency, making them ideal for server virtualization. Examples include VMware ESXi and Microsoft Hyper-V Server.

Type 2 Hypervisor (Hosted Hypervisor): Type 2 hypervisors run on top of a host operating system. They are generally used for desktop virtualization and are more suitable for testing and development environments. Examples include VMware Workstation and Oracle VirtualBox.

1.b Virtual Machines (VMs):

An actual computer system is emulated by software in a virtual machine. It includes a virtual processor, memory, storage, and network interfaces. Each VM runs its own operating system (OS) and applications, creating a self-contained environment. Multiple VMs can coexist on a single physical machine, sharing the underlying hardware resources.

1.c Host Machine:

The physical machine that hosts virtual machines is called the host machine or host server. It provides the necessary computing resources, such as CPU, memory, storage, and network connectivity, to the VMs running on it. The host machine also runs the hypervisor, managing the VMs and facilitating their operations.

1.d Guest Machine:

Each virtual machine running on the host machine is referred to as a guest machine. A guest machine behaves as an independent system, running its own OS and applications. Multiple guest machines can run concurrently on the host machine, each with its own virtualized set of resources.

1.e Resource Virtualization:

Virtualization abstracts the underlying physical resources, such as CPU, memory, storage, and networking, and presents them as virtual resources to the guest machines. Each VM is allocated a portion of these virtual resources, which it can use as if it were running on a dedicated physical machine. This allows efficient utilization of hardware resources and enables the sharing of resources among multiple VMs.

1.f Isolation and Security:

Virtualization provides strong isolation between guest machines. Each VM is encapsulated within its own virtual environment, ensuring that it operates independently of other VMs running on the same host. This isolation provides enhanced security, as any issues or vulnerabilities in one VM do not directly affect others.

1.g Live Migration:

Live migration is a key feature of virtualization that allows a running VM to be moved from one physical host to another without disruption to the services it provides. Live migration enables load balancing, resource optimization, and improved availability in virtualized environments.

2. Implementation Levels of Virtualization

Virtualization can be implemented at different levels within a computing system, each offering varying degrees of abstraction and flexibility. Here are the common implementation levels of virtualization:

2.1 Full Virtualization:

In full virtualization, the entire software stack, including the guest OS, runs on top of the hypervisor. The guest OS is unaware that it is running in a virtualized environment and operates as if it were running on dedicated hardware. Full virtualization provides the highest level of isolation and compatibility but can incur some performance overhead due to the need for hardware emulation.

2.2 Para-virtualization:

Para-virtualization involves modifying the guest OS to make it aware of the virtualization layer. The guest OS interacts directly with the hypervisor, bypassing the need for hardware emulation. This improves performance and efficiency compared to full virtualization but requires modifications to the guest OS.

2.3 Operating System-Level Virtualization:

Operating System (OS)-level virtualization, also known as containerization or container-based virtualization, operates at the OS level. It allows multiple isolated user-space instances, known as containers, to run on a single host operating system. Containers share the host OS kernel and libraries but have separate file systems, process spaces, and network interfaces. OS-level virtualization provides lightweight and efficient virtualization, with minimal overhead, as it eliminates the need for multiple OS instances. It is commonly used for deploying and managing applications in cloud environments.

2.4 Hardware Virtualization:

Hardware virtualization, also known as server virtualization, involves the virtualization of physical servers. It allows multiple VMs to run on a single physical server, with each VM having its own OS and applications. Hardware virtualization is widely used in data centers and enterprise environments, enabling efficient utilization of server resources and improved scalability.

2.4.a Server Virtualization: 

Server virtualization allows for the creation of multiple virtual machines (VMs) on a single physical server. Each VM operates as an independent system, running its own operating system and applications. Server virtualization improves resource utilization, simplifies management, and enhances flexibility and scalability.

2.4.b Storage Virtualization:

Storage virtualization abstracts physical storage components so that systems and applications can access them as logical storage units. It enables the pooling and management of storage resources from multiple physical devices, providing a unified and scalable storage infrastructure. Storage virtualization simplifies storage management, improves flexibility, and enhances data protection and disaster recovery capabilities.

2.4.c Network Virtualization:

Network services are separated from the underlying physical network infrastructure thanks to network virtualization. It enables the creation of virtual networks that are independent of the physical network topology. Network virtualization allows the provisioning of virtual networks with their own addressing, routing, and security policies, providing flexibility, scalability, and isolation in multi-tenant environments.

2.4.d  Desktop Virtualization:

Desktop virtualization, also known as Virtual Desktop Infrastructure (VDI), separates the desktop environment from the physical client device. It involves running multiple virtual desktop instances on a centralized server, which are then accessed by end-users through thin clients or other devices. Desktop virtualization simplifies desktop management, enhances security, and enables remote access and mobility.

2.4.e Application Virtualization:

Application virtualization isolates applications from the underlying operating system and hardware dependencies. It encapsulates applications and their dependencies into self-contained units, known as application containers or virtualized packages. These packages can be deployed and executed on different systems without the need for installation or modification. Application virtualization simplifies application deployment, improves compatibility, and enables application mobility.

In conclusion, virtualization is a foundational concept in modern computing, enabling the efficient utilization of resources, flexibility, and scalability. It abstracts and isolates resources, creating virtual environments that behave as independent systems. Virtualization can be implemented at various levels, including full virtualization, para-virtualization, OS-level virtualization, hardware virtualization, storage virtualization, network virtualization, desktop virtualization, and application virtualization. Each implementation level offers different levels of abstraction and flexibility, catering to specific use cases and requirements.

3. From Virtualization to Cloud Computing:

Virtualization laid the foundation for cloud computing. Cloud computing takes virtualization a step further by leveraging virtualized resources to deliver on-demand services over the internet. Cloud providers use virtualization to create and manage multiple virtual machines and offer various cloud services, such as Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

Virtualization enables cloud providers to optimize resource utilization, rapidly scale services, and offer flexible, cost-effective solutions to customers. Cloud computing builds upon virtualization by providing a range of self-service, scalable, and pay-as-you-go services accessible to users worldwide. It has revolutionized the way IT resources are provisioned and managed, enabling organizations to focus on their core business while relying on cloud providers for their computing needs.