Understanding Virtualization: A Comprehensive Overview

With the rise of technologies such as virtualization and cloud computing,IT has once again redefined virtualization technology, which has a history of several decades, expanding its scope. However, to date, there is no universally accepted standard definition of virtualization; most definitions are based on its applications. Generally, virtualization can be summarized and described as: a logical abstraction of physical resources.

Definition of Virtualization

In response to the rapidly evolving virtualization technology, some global standard organizations and large companies have provided their definitions of virtualization. Below are some excerpts:

The definition by IBM is: “Virtualization is a logical representation of resources, unconstrained by physical limitations.”

The definition by Wikipedia is: “Virtualization is the process of presenting computer resources as a logical group (or subset) so that they can be accessed in a way that benefits from the original configuration. This new virtual view of resources is not limited by implementation, geographical location, or the physical configuration of underlying resources.”

Jonathan Eunice’s definition is: “Virtualization is the process of representing computer resources in a way that users and applications can easily benefit from, rather than representing them in a proprietary way based on their implementation, geographical location, or physical packaging. In other words, it provides a logical view of data, computing power, storage resources, and other resources, rather than a physical view.”

Development Process of Virtualization

Christopher published a paper titled “Time Sharing in Large High-Speed Computers” in 1959, which is considered the first article to use the term virtualization. Since then, virtualization has entered a rapid development phase.

The development process of virtualization can be described as a progression from mainframes to minicomputers to x86 servers, driven by the need to fully utilize hardware resources through software and hardware solutions.

In the 1960s, IBM addressed the issue of underutilization of expensive mainframe resources by logically partitioning the mainframe, allowing multiple applications to run within their respective partitions without interference, forming the prototype of virtual machines.

Subsequently, IBM introduced the Virtual Machine Monitor (VMM) and Virtual Machine (VM) technology, providing an independent computing environment and virtual machine instances for mainframe usage. IBM’s Logical Partitioning (LPAR) technology has continuously evolved virtualization technology and has been applied on minicomputers.

Servers have evolved from mainframes and minicomputers to the development and popularization of PC servers, becoming increasingly segmented. With the rise of graphical operating systems like Windows and the rapid development of Linux due to its free nature, x86 architecture PC servers gradually replaced minicomputers, becoming the mainstream in the server market. Virtualization technology for x86 architecture servers has also achieved rapid development. In 1999, VMware launched the first virtual machine based on x86 systems.

In today’s Internet era, virtualization technology is no longer limited to the server domain; it has been widely applied in networking, storage, and desktop applications, forming various development directions for different virtualization technologies.

Virtualization Direction — Cloud Computing

In the context of today’s rapid development of software and hardware technologies, virtualization technology can flexibly respond to the rapidly changing business needs of users, enabling flexible resource deployment and effectively improving resource utilization. Therefore, virtualization technology has become one of the fastest-growing fields, serving as a core technology of cloud computing. With virtualization technology as support, cloud computing has achieved remarkable results in the Internet domain.

Working Modes of Virtualization

Based on different technical implementations and logical representations of supported resources, virtualization working modes can generally be divided into three types.

1. One-to-Many Mode

This is the most common virtualization mode, where multiple logical structures are implemented on a single physical resource. It logically represents a single physical resource to provide users with multiple virtual resources that share the same attributes as the physical resource, where each logical resource user believes they are exclusively using the entire physical resource. The primary goal of this mode is to ensure that powerful devices’ resources can be fully utilized. Virtual servers are typical representatives of this mode. By installing virtualization software on one or several physical servers, numerous logical units can be virtualized, each capable of installing different operating systems and performing different tasks.

2. Many-to-One Mode

This mode can be described as organically integrating multiple or different groups of physical resources, presenting them logically through a single interface. The primary aim is to provide a strong resource pool by integrating ordinary resources to achieve higher performance. Storage virtualization is a typical representative of this mode. Different types of storage can be connected together through relevant software and hardware to merge into a large unified storage pool, where data is stored within this pool and distributed across different storage devices. However, for data operators, this is transparent; they do not know which storage device the data is actually stored on. Server clustering technology and grid computing also utilize this mode.

3. Many-to-Many Mode

This mode describes multiple physical resources storing identical copies of a unified logical unit. In practical applications, requesters select a physical resource based on specified conditions to meet their needs. Compared to the second mode, this mode represents a single physical resource as merely a copy of the same resource; they cannot logically cluster together for expression. Each physical resource contains all the logical functions and forms a replication relationship among multiple physical resources. A typical application of this mode is file virtualization, where when users access a specific file, the system locates a physical resource for reading based on internal rules, without the user knowing which physical resource they accessed.

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