Virtualization

History of virtualization:

Virtualization was started way back in 1960's by IBM as an architechture for then emerging time share system concepts. The main machine was an IBM 7044 (M44) and each virtual machine was an image of the main machine (44X).

Definition:

Virtualization is loosely defined as a framework or methodology of dividing the resources of a computer into multiple execution environments, by applying one or more concepts or technologies such as hardware and software partitioning, time-sharing, partial or complete machine simulation, emulation, quality of service, and many others.

Server Virtualization

Enterprises require more number of servers when they implement new applications or enhance the existing applications. To maintain cost and to maximize the utilization of servers, enterprises can make their servers virtual. Server virtualization is the practice of dividing one physical server into many isolated virtual environments.

Uses of server virtualization:

• Consolidation of servers: As the number of applications increases, number of servers also increases and this results in more utilization of physical space. Server virtualization reduces the physical space through consolidation of several machines into one server.
• Redundancy without additional investment: Without investing in additional hardware, with server virtualization companies can run same application on different physical servers. This redundancy practice will minimize service interruption.
• To test applications: With server virtualization, programmers can test new application or operating systems without affecting the performance of other applications.
• Hardware virtualization: Server hardware has a short life span and becomes obsolete relatively quickly. Another advantage of virtualization is that it facilitates the movement of older hardware to newer hardware.
• Migration: With virtualization it is possible to move virtual servers from one machine to another. This is called migration and it is possible if processors on both the machines are from the same manufacturers.
  

Reference:

http://communication.howstuffworks.com/server-virtualization.htm/printable

http://www.kernelthread.com/publications/virtualization/