Virtual machines are used to consolidate many physical servers into fewer servers, which in turn host virtual machines. Each physical server is reflected as a virtual machine "guest" residing on a virtual machine host system. This is also known as Physical-to-Virtual or 'P2V' transformation.
Virtual machines can be used as "hot standby" environments for physical production servers. This changes the classical "backup-and-restore" philosophy, by providing backup images that can "boot" into live virtual machines, capable of taking over workload for a production server experiencing an outage.
Testing and training
Hardware virtualization can give root access to a virtual machine. This can be very useful such as in kernel development and operating system courses.
The Microsoft Windows platform has a well-known issue involving the creation of portable applications, needed when running an application from a removable drive, without installing it on the system's main disk drive. This is a particular issue with USB drives. Virtualization can be used to encapsulate the application with a redirection layer that stores temporary files, Windows Registry entries, and other state information in the application's installation directory – and not within the system's permanent file system. See portable applications for further details. It is unclear whether such implementations are currently available.
Recent technologies have used virtualization to create portable workspaces on devices like iPods and USB memory sticks. These products include:
- Application Level – Thinstall – which is a driver-less solution for running application directly from removable storage without system changes or needing Admin rights
- OS-level – MojoPac, Ceedo, and U3 – which allows end users to install some applications onto a storage device for use on another PC.
- Machine-level – moka5 and LivePC – which delivers an operating system with a full software suite, including isolation and security protections.
Operating System Virtualization and Application Virtualization
Database \ Data Virtualization
images courtesy of :windowsecurity.com