Ways to Virtualize the Client Desktop in Cloud Computing
1 of 4 in Series: The Essentials of Desktops in Cloud Computing
In a virtualized desktop in cloud computing, the applications, data, files, and anything graphic are separated from the actual desktop and stored on a server in a data center (not on the individual machine). Virtualizing the desktop can bring down the total cost of ownership, because it helps manage and centralize support. Standardizing infrastructure that needs to be managed via virtualization makes it easier to optimize IT resources.
Virtualizing the client desktop can happen four ways. You could loosely describe every one of these techniques as client virtualization, because in each technique the PC is controlled from the data center (not from the desktop). In practice, however, only one of these techniques, VDI, is based on true virtualization, which is the use of software to emulate a computing environment within another computer.
Client virtualization involves emulating a whole PC in software on a data center server and displaying the user interface on a graphics terminal.
Computers have become powerful enough to do this, and users are unlikely to detect the difference between client virtualization and a desktop.
In session-based computing, the user is really running a session on a server. The server is running a single instance of the Windows operating system with multiple sessions. Only the screen image is actually transmitted to the user, who may have a thin client or possibly an old PC.
In this approach, the Windows OS software is passed to the client device, but only as much of the software that’s needed at any point in time. Technically, this process is called streaming.
Some of the processing occurs on the disk and some in local memory. Thus, the Windows OS and its applications are split between the client and the server. Streaming applications run at about the same speed as reading the application from the disk.
Virtual Desktop Infrastructure
Here, virtual PCs (complete emulations of a PC) are created on the server. The user has what appears on the server to be a complete PC. The graphics are being sent to a desktop. Today, most people refer to this kind of client virtualization as Virtual Desktop Infrastructure (VDI).
VDI is the ability to have shared client sessions on the server rather than on the client. The software you need to use sits on the server and an image can be viewed on your device. It is a type of virtualization hosted on the server. It's widely used and appropriate in many client environments.
The PC blade
A server blade is a server computer contained entirely on a single computer board that can be slotted into a blade cabinet, a purpose-built computer cabinet with a built-in power supply. The server blade can contain a number of PC blades.
Each user is typically associated with one PC blade, although some environments let multiple users share one PC blade, and a whole PC sits on a server blade in the data center. Normally, the desktop is a thin client.