Application Virtualization

Application Virtualization is an umbrella term that describes software technologies that improve portability, manageability and compatibility of applications by encapsulating them from the underlying operating system on which they are executed. A fully virtualized application is not installed in the traditional sense, although it is still executed as if it were. The application is fooled at runtime into believing that it is directly interfacing with the original operating system and all the resources managed by it, when in reality it is not. In this context, the term "virtualization" refers to the artifact being encapsulated (application), which is quite different to its meaning in hardware virtualization, where it refers to the artifact being abstracted (physical hardware).

Desktop Virtualization

Desktop virtualization involves encapsulating and delivering either access to an entire information system environment or the environment itself to a remote client device. The client device may use an entirely different hardware architecture than that used by the projected desktop environment, and may also be based upon an entirely different operating system.

The desktop virtualization model allows the use of virtual machines to let multiple network subscribers maintain individualized desktops on a single, centrally located computer or server. The central machine may operate at a residence, business, or data center. Users may be geographically scattered, but all may be connected to the central machine by a local area network, a wide area network, or the public Internet.

Server Virtualization

Server virtualization is the masking of server resources, including the number and identity of individual physical servers, processors, and operating systems, from server users. The server administrator uses a software application to divide one physical server into multiple isolated virtual environments. The virtual environments are sometimes called virtual private servers, but they are also known as guests, instances, containers or emulations.

Storage Virtualization

Storage virtualization is a concept and term used within computer science. Specifically, storage systems may use 'virtualization' concepts as a tool to enable better functionality and more advanced features within the storage system. Broadly speaking, a 'storage system' is also known as a storage array or Disk array or a filer. Storage systems typically utilize specialized hardware and software along with disk drives in order to provide very fast and reliable storage for computing and data processing. Storage systems are complex, and may be thought of as a special purpose computer designed to provide storage capacity along with advanced data protection features. Disk drives are only one element within a storage system, along with hardware and special purpose embedded software within the system. Storage systems can provide either block accessed storage, or file accessed storage. Block access is typically delivered over Fibre Channel, iSCSI, SAS, FICON or other protocols. File access is often provided using NFS or CIFS protocols.

Within the context of a storage system, there are two primary types of virtualization that can occur:

Block Virtualization

Block virtualization used in this context refers to the abstraction (separation) of logical storage from physical storage so that it may be accessed without regard to physical storage or heterogeneous structure. This separation allows the administrators of the storage system greater flexibility in how they manage storage for end users.

File Virtualization

File-level virtualization addresses the NAS challenges by eliminating the dependencies between the data accessed at the file level and the location where the files are physically stored. This provides opportunities to optimize storage utilization and server consolidation and to perform nondisruptive file migrations

Network Virtualization

Network Virtualization is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization.

Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to the software containers on a single system. Whether virtualization is internal or external depends on the implementation.