Making the Switch to Desktop Virtualization
Why it’s important and how to do it right
By: Stephen Yeo
May. 5, 2009 01:45 PM
Traditionally, organizations have had two choices for delivering a PC application: a "fat" PC or server-based terminal services. Terminal services is an approach that hosts the application in an x86 "mainframe" environment, collects keystrokes and mouse clicks from the user, and delivers the resulting screen changes back to the user using a bandwidth-efficient protocol such as RDP or ICA. A small piece of client software running on a thin client or an old PC would decode the instructions and "draw" the screen changes on the monitor. The leading solutions for terminal services software include Microsoft Windows Server (with its terminal-services mode) and Citrix Metaframe.
Now there's a new way to deliver PC applications - a virtual PC. Virtualization is a process that can break a physical server into lots of smaller machines. The software that does this is called a hypervisor and many companies produce them, including VMware, Citrix, Microsoft, Oracle, and Sun. Once a hypervisor is installed on an x86 server, a systems administrator can create virtual machines that can then be treated as virtual PCs. Any x86 operating system such as Microsoft Windows XP or Vista can then be installed and accessed using its built-in RDP connection.
Why Is Desktop Virtualization Important?
Terminal services solved many of the fat PC issues, but it had a few important issues of its own. First, like it was designed, it behaved like a mainframe running Windows. Users couldn't customize their desktops or easily install new applications or peripherals. Second, the terminal services architecture was fundamentally different from a traditional PC. Like a mainframe, the server shared a single instance of an application with the many users accessing it. That's why terminal services is sometimes referred to as "shared-mode" delivery. Unfortunately, about 10% of PC applications didn't like being shared and would refuse to run in a terminal services environment. This meant that many organizations kept their old PCs as a "safety net for the problem children"; removing the ability to access all applications with thin clients. Not being able to use thin clients removed more than 50% of all the total cost of ownership (TCO), security, and management benefits available in a fully centralized thin IT architecture.
Virtual PCs deliver the TCO, security, and manageability benefits of terminal services, but behave just like a PC since no application is shared. This means organizations can now move to server-based computing faster and with less risk than before. It also opens the flood gates for thin clients on the desktop since it removes the need to keep the fat PC as a safety net. This means organizations opting for virtual desktops can reclaim the 50% of additional cost savings, management, energy, and security benefits that most terminal service users could never claim since they couldn't "kick the habit" of using fat PCs as access devices.
Making the switch to thin clients using a virtualized desktop can also drastically reduce the CO2 emissions attributed to PC manufacturing and usage. According to a recent study by the Fraunhofer Institute for Environmental, Safety, and Energy Technology (UMSICHT), replacing a PC with a thin client reduces the emissions of a workstation by more than 54%. For a company with 300 workstations, the use of thin clients can save more than 148 tons of CO2 emissions over a five-year period. (A Volkswagen Golf TDI could drive more than 1,090,000 km - and circle the earth 27 times - with this volume of emissions.) This means that during a five-year lifecycle (including production, operation, and disposal), thin clients are both more environmentally friendly and more economical than PC workstations.
One final important factor with desktop virtualization is that the hypervisor is an ideal technology for dividing up all the power of modern microprocessors. Massively multi-core CPUs are starting to arrive and can provide far more horsepower than a single end user can consume.
Hypervisors divide these MPP machines into more manageable chunks that can provide single users with all the computing power they need. It means that operating systems like XP Professional, originally limited to dual-CPU systems, can still be used effectively on massively multi-core processors.
These considerable benefits of virtualized desktops are why Credit Suisse thinks the virtual PC market will be worth at least $1.5 billion by 2011, representing 25.6 million users or 5.7% of the professional desktop installed base.
What Are the Limitations of Desktop Virtualization?
The main limitation of virtual PCs is that, unlike physical PCs, they rely on a single protocol (RDP or ICA) to deliver the whole PC experience through a network. That means a virtual PC has to translate into RDP/ICA before network transmission all the different delivery protocols being used to deliver the user experience, such as HTML, Flash, or SIP (the VoIP protocol). This translation can result in a greatly degraded application experience and limits the freedom of IT managers when designing their virtual desktop infrastructures.
Another limitation with this "all roads lead to the virtual PC" approach is that it causes problems for latency-sensitive applications such as VoIP or video conferencing since no peer-to-peer traffic is possible. For example, a VoIP call within the same New York office would have to go via the Singapore data center.
A final issue with virtual PCs is that they are just another way of delivering Win32 applications and many new applications are delivered in ways that don't need Win32. For example, more than 50% of corporate applications now use a Web interface for access. A virtual PC is a very expensive and complex way to deliver access to an application that relies on a Web browser, Java Virtual Machine, or terminal emulator.
How to Overcome the Limitations of a Virtual PC
First, there are now multimedia re-direction solutions that will take certain protocols, like .wav or .mpg files, outside the normal ICA/RDP channel. When a user triggers certain multimedia applications on his virtual PC, special server-side software detects this and transmits the multimedia content via a separate channel to the end-user device. The Windows desktop is then seamlessly rebuilt by combining the ICA/RDP and multimedia input.
An alternative, more flexible approach is not to translate all the different application protocols in the first place. You can do this by using a modern thin client that contains all of the different protocols, or digital services, that are used to deliver modern server-based applications. This "universal desktop" approach means that a thin client always has the right digital services for the job including ICA/RDP, Web browser, Flash, JVM, terminal emulation, VoIP client, and SAP GUI. Putting the digital services as close to the user as possible means IT managers are never limited in how they can deliver a centralized application. The device is still a thin client with no moving parts, local applications, or data. It can be used to access a virtual PC in a highly centralized environment, while still being able to make local VoIP calls with little latency, for example.
The user experience is taken to the ultimate level with the introduction of Digital Services Virtualization (DSV), which lets you deploy the toughest server-based computing environments with an experience that is indistinguishable from a traditional PC, including all multimedia, VoIP, video conferencing, local device control such as CCTV and industrial automation, and embedded DirectX local applications on Windows XP Embedded.
This is done by reverse publishing the digital services on a universal desktop out onto the cloud on the virtual PC. This innovative approach offers an outstanding user experience with a standard PC desktop look-and-feel, all local digital services controlled from the virtual desktop, and no need to "toggle" between digital service sessions. Local digital services can communicate directly via the native protocol designed for the application without having the bottleneck of delivering everything down the ICA or RDP protocol. With DSV once the key digital services have been reversed-published onto the virtual PC, if, for example, a user opens a Web browser by clicking on the Web browser icon on the virtual PC, a command is automatically sent to the universal desktop and the local Web browser is opened directly including Flash, multimedia, etc. This is all done seamlessly without any impact to the user, providing an experience that is indistinguishable from a traditional PC.
By moving as many digital services as possible off the virtual PC to the universal desktop, the virtual PC can be avoided altogether in certain situations that don't need a Win32 environment. This can potentially save more than $500 per user in hardware and software costs alone - more than the price of a thin client.
Fortunately, these issues can be overcome relatively easily and they pave the way for virtual desktops and thin clients to offer an equivalent experience as the traditional fat desktop - but without the hassles, complexity, and costs.
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