Intro to virtualization

From Wikipedia, the free encyclopedia

In computing, virtualization is a broad term that refers to the abstraction of computer resources:

• Virtual machine (VM), a software implementation of a machine (computer) that executes programs like a real machine

• Platform virtualization, which separates an operating system from the underlying platform resources

• Full virtualization, sensitive instructions replaced by binary translation or trapped by hardware - all software can run in the VM, e.g. IBM's CP/CMS, VirtualBox, VMware Workstation
• Hardware-assisted virtualization, CPU traps sensitive instructions - runs unmodified guest OS; used e.g. by VMware Workstation, Xen, KVM
• Partial virtualization, for specific applications rather than the operating system
• Paravirtualization, a virtualization technique that presents a software interface to virtual machines that is similar, but not identical, to that of the underlying hardware, thereby requiring guest operating systems to be adapted
• Operating system-level virtualization, a method where the operating system allows for multiple user-space instances (virtual hosting, chroot jail + resource management)

• Application virtualization, the hosting of individual applications on alien hardware/software

• Portable application, a computer software program that runs from a removable storage device as a USB flash drive
• Cross-platform virtualization, allows software compiled for a specific CPU and operating system to run unmodified on different CPUs and/or operating systems
• Virtual appliance, a virtual machine image designed to run on a virtualization platform
• Emulation or simulation

• Virtual memory, which allows uniform, contiguous addressing of physically separate and non-contiguous memory and disk areas
• Storage virtualization, the process of completely abstracting logical storage from physical storage
• Network virtualization, creation of a virtualised network addressing space within or across network subnets
• Virtual private network (VPN), a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network(s), such as the Internet
• Memory virtualization, aggregates RAM resources from networked systems into virtualized memory pool
• Desktop virtualization, the remote manipulation of a computer desktop
• Timeline of virtualization development, further work in this area