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Virtualization refers to running multiple virtual computers, or virtual machines, inside a single physical computer. While the basic idea of virtualization is old (dating back to mainframe computers in 1960s), it has become mainstream only in the last 10-15 years. Today, most new servers are virtualized.

  • Hypervisor is the operating system running on actual hardware. Virtual machines run as processes within this operating system. Sometimes the hypervisor is called Dom0 or Domain 0.
  • Virtual machine is a virtual computer running under a hypervisor.
  • Container is a lightweight virtual machine that runs under the same operating system instance (kernel) as the hypervisor. Essentially, a container is nothing but a group of processes with their own name space for process identifiers etc.
  • Virtual network is a logical network within a server, or possibly extending to multiple servers or even multiple data centers.
  • Virtualization software is software that implements virtualization on a computer. It can be part of an operating system (or a special version of an operating system) or an application software package.

Virtualization is the basis of modern cloud computing.

Why Virtualize?

Virtualization drivers in recent years have included:

  • More powerful hardware, allowing each machine to run multiple applications simultaneously
  • Pressure to lower IT costs and simplify IT administration
  • Need to manage large-scale installations and clusters, such as server farms
  • Improved security, reliability, scalability, and device independence
  • Ability to mix multiple operating systems on same hardware.