Virtualization (or Virtualisation) is a word used in computing. Virtualization means that the users (programs, or real people) only see an abstraction of a computer resource. Virtualization can be done in software, or with hardware.
- RAID. RAID is used to virtualize computer storage. A RAID system appears as one "disk". The fact that it is made of several disks that work together is hidden.
- Virtual memory makes it possible to use more memory than is physically in the computer. The computer figures out a way to write contents of certain memory blocks to disk.
- Storage virtualization takes the ideas developed by RAID further. This is what Storage area networks commonly use. All the storage appears as a single big disk. Certain administrators can specify that this large disk is made of "data pools" (which are also virtual). The disk pools are made of single physical disks (or RAID arrays).
- Some computers (mostly mainframes) allow to run several operating systems at the same time. Each operating system believes it is the only one running.