Virtualization is a broad term that refers to the abstraction of computer resources. Virtualization hides the physical characteristics of computing resources from their users, be they applications, or end users. This includes making a single physical resource (such as a server, an operating system, an application, or storage device) appear to function as multiple virtual resources; it can also include making multiple physical resources (such as storage devices or servers) appear as a single virtual resource.
The term has been widely used since the 1960s, and has been applied to many different aspects and scopes of computing—from entire networks to individual capabilities or components. The common theme of all virtualization technologies is the hiding of technical detail, through encapsulation. Virtualization creates an external interface that hides an underlying implementation (e.g., by multiplexing access, by combining resources at different physical locations, or by simplifying a control system). Recent development of new virtualization platforms and technologies has refocused attention on this mature concept.
Virtualization is used in many different contexts, which can be grouped into two main types: platform virtualization, involving the simulation of whole computers, and resource virtualization, involving the simulation of combined, fragmented, or simplified resources.
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