A

Application Streaming Streaming is a transport technique where applications or elements of an application are transferred to a remote client, then read, interpreted, and run in real time. Media streaming is commonly used to show videos or play audio, and application streaming generally allows applications to start remotely (with minimal code present), while other code is transferred to the client in the background (and is then ready to use when needed).

Application Virtualization Application virtualization is the separation of the application from OS and applies to applications on all tiers from servers down to desktops (where applications or application components run). This is generally accomplished through encapsulation. Encapsulation and isolation from the underlying OS changes the paradigm of how applications install and interact with the OS. This allows applications to be easily moved from system to system, patched or updated without interference to other applications or the OS and co-exist with other applications without conflict. Additionally applications can be copied, backed-up, or archived just as a single file can and be controlled and monitored. Application virtualization is the technology that truly separates the infrastructure (servers and OS) lifecycle from the application lifecycle.

C

Capsules A capsule embodies an isolated application and all of its dependencies, such that an application embodies in a capsule can run on any host OS in the family, regardless of the specific OS personality. With encapsulation the application's dependency on the OS has been neutralized.

E

Encapsulation Encapsulation is the process of defining an application and all of its dependencies, then locating them under one physical and isolated folder or entity.

G

Grid Computing Grid computing is a distributed computing technique where disparate computing (and storage) resources are organized to perform a computing task. The computing resources can be remotely federated through the Internet or other more secure networks. Much like a utility company's power grid, a computing grid can be used simultaneously by various users with varying computing requirements. Grid computing is often used to tackle computations of enormous scale that could not easily be completed by super computers.

H

Hardware Virtualization This describes technology that emulates hardware to enable multiple operating systems to co-exist on the same platform. Typically a hypervisor is used to deliver the hardware emulation. With hardware virtualization a complete OS is run in each virtual session including kernel, directory structures and user mode OS services.

Hypervisor A hypervisor exists as a control layer between the hardware operating system(s). A hypervisor allows multiple operating systems to run on the same physical hardware. There are two common types of hypervisor architectures; bare-metal or hosted. Bare-metal architecture enables the hypervisor to run directly on the hardware (with no other OS needed).

In a hosted architecture (type 2) the hypervisor resides on top of an existing installed OS, which in turn hosts guest OSs above it (total of three layers).

N

Network Virtualization Network virtualization is the use of logical network entities that utilize the underlying physical components of the network. The original network virtualization technology is the Virtual LAN (VLAN). This networking technology maps two disparate networks into a single, unified logical network entity. The VLAN is used in such a way that makes it appear as though everything was physically located together, though in reality, there may be remote connections defined. This same technology can be used to segment one contiguous network system. Applications or services in the server are given unique network identities, and routing within the server is handled along with networking protocols. The use of networking protocols effectively isolates the applications and services, often making them easier to monitor and manage.



O

OS Virtualization OS virtualization is the creation of separate and partitioned run-time environments all within the same overall OS. The way that applications are installed and interact with the OS is not changed, so there are no changes of substance to the application lifecycle. These separate runtime environments rely on a single kernel instance and managed by the host OS each partition in the system shares that kernel. Much of the OS user space, though not the kernel, is replicated in each partitioned runtime environment. Solaris Containers and Zones are one of the better known OS virtualization environments.

P

Para-virtualization Para-virtualization is a virtualized server technique that emulates real or fictional hardware for a modified guest OS. The para-virtualized server is a modified guest OS running on top of the hypervisor (virtual machine monitor). The guest OS has been modified so that the guest OS makes system calls directly to the hypervisor (not executing I/O instructions directly to the machine), and the hypervisor simulates the machine feedback (and negotiates with the actual machine).

The main difference between a virtual machine and para-virtualization is that the guest OS on a virtual machine is an unmodified off-the-shelf product, but the guest OS in para-virtualization is modified to work more directly with the hypervisor.

Physical to Physical Migration Physical to physical migration (P2P) defines the process of moving a complete OS environment, and the installed applications, from one physical server to another physical server. This is done by cloning drives and putting the cloned drive into a new server, using server virtualization as an intermediate process, or by using application virtualization to easily control the movement of applications from one physical environment to another.

Physical to Virtual Migration Physical to virtual migration (P2V) defines the process of capturing and migrating a complete OS environment, and the applications installed on it from a physical server to a virtual environment.

S

Server Virtualization Server virtualization is a generalized term describing the ability to host multiple complete OS images (including or excluding a kernel) on a single hardware platform. Both OS virtualization and hardware virtualization technologies result in the creation of a virtual server. The way that the OS interacts with the hardware platform is modified so that multiple OS instances can share the underlying hardware platform. Server virtualization is often used to consolidate multiple smaller (or older) servers onto a single, large server, without changing how the applications or OS is managed.

Storage Virtualization Storage virtualization is the abstraction of the physical storage from the logical storage. While the actual physical storage may include several separate storage devices of different capacity and performance, storage virtualization presents a single logical storage entity. This means that the Storage Area Network (SAN) may consist of storage pools and storage devices in different locations at the physical level, but the user would see a single (often very large) storage entity, which can, from the user perspective, be managed centrally as well.

U

Utility Computing Utility computing is a metered service where computing or storage resources are provided on a needed basis similar to the way public utilities (water, electricity, telephone, etc.) are provided to homes and paid for as they are used. The purest form of utility computing requires two service characteristics metered billing and dynamic resource allocation. Customers of utility computing are not billed for a specific computer or server but are billed just for the computing or storage facilities and cycles used. In the simplest terms, utility computing implies the capability to use more resources temporarily and on-demand during peak periods.

V

Virtual Desktop Virtual desktops separate the classic PC desktop from the PC. Rather than reading the OS desktop on the PC, the user is accessing a virtual instance of the desktop, usually remote from the user and PC. This means that PCs (or even terminal) act merely as a KVM (keyboard, video display, and mouse) over a network to a centrally hosted desktop. This separation gives flexibility to the user, as they can access their desktop from any machine with network connectivity to their server. This separation allows many economies of scale and standardization for IT when it comes to desktop management.

Virtual Machine A virtual machine is a virtualized server emulating real or fictional hardware for an unmodified guest OS. The virtual machine is installed as an application on the host OS. Applications are installed normally in the virtual machine environment, and are unaware that they exist on a virtual machine (as opposed to a physical machine) – all of the OS duties needed by the application are performed by the virtual machine (not the host OS).

Virtual to Physical Migration Virtual to physical migration (V2P) describes the process of installing a virtual environment (i.e., virtual machine) onto a physical server.