Virtualization Technology: Types, Modes & Terms

Instructor: Muhammad Wannous

Muhammad has been teaching Computer Sci. and Eng. and has a Ph.D. degree in Computer Sci. and Electrical Eng.

Imagine a Linux instance running side by side with a Windows one, on a single computer, at the same time! Virtualization technology makes this possible. In this lesson you will study more about virtualization technology and the different concepts associated with it.

Virtualization in Brief

In Computer Science the term virtualization refers to the partitioning of physical resources into multiple virtual resources (software-based). A virtual resource can provide the functions of the physical one but it has less capacity or capability. A combination of virtual resources form a complete machine, normally referred to as a Virtual Machine (VM) , which simulates the original hardware formed by the physical resources.

Virtualization has become very popular among both service providers and end-users. It serves in creating multiple computers, or VMs, that can run on one physical platform. So, if you have a powerful laptop, you can turn it into a number of lower capacity laptops to perform more functions with them.

Figure-1: Concept of Virtualization Technology
Concept of Virtualization Technology

Virtualization Timeline

Virtualization development started back in the 1960s with the aim to share the then expensive computing resources among a large number of users. Batch processing was a common model for processing users' requests in the business sector. However, the rise of single-user machines and the spread of other solutions to the single-machine-multiple-users problem caused virtualization technology to fade out. This situation remained unchanged until the 1990s when most IT companies had their infrastructures from single-vendors and wanted to run more powerful operating systems and applications from multiple makers. The task was challenging because the run-environment may vary for each application while the underlying infrastructure is fixed. Thus, virtualization technology returned back into the scene to help address this issue.

Benefits of Virtualization

In a situation where it is necessary to run a number of applications that demand different environments, IT companies opt to group the applications based on their requirements and run each group on a separate machine as in Figure-2 (a). The other option that virtualization technology introduces is the partitioning of one physical server resources among a number of VMs and running the applications inside them as shown in Figure-2 (b).

Figure-2: Two Options to Run Applications of Different Requirements
Two Options to Run Application of Different Requirements

The benefits of adopting virtualization technology from different aspects are shown in Table-1.

Table-1: Benefits of Virtualization

Aspect The solution NOT adopting virtualization The solution adopting virtualization
Resource Utilization Dedicated physical hardware assigned to run a small group of applications leading to resource under-utilization Virtual resources assigned based on the application requirements leading to higher utilization of resources
Consolidation A number, normally large, of physical machines requiring space and power Fewer physical machines requiring less space and power
Workload Migration Only possible between machines of the same specifications and run-environment VMs can be migrated between physical servers regardless of their hardware specifications

Virtualization has reduced our dependency on the vendors and has become the foundation technology of Cloud Computing, the computing environment offering resources and services as per the consumers' needs.

How Virtualization Works

In a machine where virtualization technology is not adopted, the operating system runs on top of the hardware resources and manages a number of applications as demonstrated in Figure-3. The operating system, in this case, has control over the resources and regulates access to them allowing a number of applications to run concurrently.

Figure-3: The Organization of a Machine where Virtualization is NOT Adopted
The Organization of a Machine where Virtualization is NOT Adopted

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