Citrix XenDesktop 5: Intro to Desktop Virtualization Part 2

Posted on October 6, 2011 by Elias Khnaser in Virtualization with

Introduction to Desktop Virtualization – Part 2

A closer look at the different types of Desktop Virtualization

In Part I of this article, we gave you a brief introduction to desktop virtualization and some very brief descriptions of each type of Desktop Virtualization.
In this article, we’ll be taking a much closer look at what each type can offer, their benefits, as well as the types of users they are best suited for.

(Instructional video below provides a walkthrough of the steps contained in this article.)

Importance of user profiling

Before you go out and invest on any desktop virtualization technology, you need to examine the types of end users your organization has and then profile them. The reason why you have to go through this is because each desktop virtualization type caters to a specific group of users.

Take a look at the diagram below.

user profiling

To simplify, your company may have power users, terminal users, mobile users, and so on.

As you can see, server-side computing types like Terminal Server and VDI are best suited for task users.  These are users who do the same tasks and use the same applications every single day. In addition, the applications they use may not be memory or CPU-intensive.

Client-side computing types like Client Hypervisor and Streaming, on the other hand, work best for users who need richer user interfaces. Notice also that Application Virtualization may cater to all kinds of users. After we discuss the different types of desktop virtualization, you can use the knowledge you’ll learn there when the time comes to profile your users.

VDI (Virtual Desktop Infrastructure) a.k.a. Server-Hosted Virtual Desktops


As its other name (Server-Hosted Virtual Desktops) suggests, VDI relies on virtual machines residing on servers. These servers can be ESX, XenServer, or Hyper-V servers housed in a data center. In other words, it follows a server-based computing model.


These are some of the benefits you can get from a VDI environment:

Centralized management and better security

Instead of managing hundreds or even thousands of computers scattered all over your premises or even across a certain geographical location, you will now be able to manage all those desktops in one central location.

In relation to that, your users will be connecting to the same central location to access their desktops. If you have centralized access, it would be much easier to enforce security measures. With all these regulations going on that affect data security, it would now be easier for you to comply.

If you have certain applications that require a high level of security and you want to allow access only to a specific set of users, then VDI is an ideal solution because you can easily control user access to a particular VM.

Existing hardware can still be used and broken hardware can be replaced with Thin Clients

In a VDI environment, much of the computing goes on in the server side. So you don’t really need powerful computers for your end users. In fact, you can still make use of existing hardware that may have been with you already for the past couple of years or so.

In addition to that, if your old hardware breaks down, you can always replace it with a thin client. Essentially, you can have a mixture of old and new hardware plus some thin clients. Thus, you can extend the lifetime of your computers.

Power savings 

Now, because you won’t be needing powerful computers, you’ll be able to save on energy consumption. Not only will you be saving dollars, you’ll also be saving the environment.

Save on support

In a traditional set up, you would need to spend time and money each time a computer in your office breaks down. You would need to send a technician to the site and the affected employee will have to be unproductive while troubleshooting is being done. By comparison, if you have a VDI setup and the problem is in the hardware, you simply replace the hardware, connect it to a VM, and your user is ready to go.

Supports disaster recovery and business continuity

Because these virtual desktops are essentially data files, you can easily perform backups and replication on them. Similarly, they are also easier to put back into operation after a disruption. In other words, VDI supports disaster recovery and business continuity.

As a matter of fact, you really need desktop virtualization to carry out true business continuity. What good would it be if you could quickly recover your data but couldn’t let your users get back to work right away because their desktops are still down?

Features device independence

VDI can serve your desktop to a variety of devices. You can access those virtual desktops from laptops, netbooks, desktop PCs, tablets, smartphones, and so on.

Once you’ve determined that VDI is appropriate for you and decide to go for it, make sure you have the following resources: adequate storage, user personalization, and – of course – the right management skills for this technology.

You’ll need sufficient storage to support all the dedicated VMs that will be running simultaneously.

It’s also equally important to support user personalization. In fact, user personalization should be supported on any desktop virtualization solution.

Regardless of the policies you set in your organization, users will always want to have some degree of personalization when using a computer. If you don’t allow your users to have some level of flexibility on their desktops, they might feel excessively constrained and that could affect their productivity.

Terminal Server

Terminal Server

As it is the oldest, most established form of desktop virtualization out there, you can be sure that practically all of the quirks and bugs associated with terminal server have already been identified and perhaps even ironed out. Thus,  with terminal server, you’ll be dealing with a relatively stable and predictable DV platform.

The other benefits of terminal server have already been tested and proven by many companies. Here are some of them:

Server-based platform benefits

Just like VDI, Terminal Server will allow you to operate thin clients alongside old and new computers. Thus, the cost-saving benefits of VDI mentioned earlier also apply to Terminal Server. And because Terminal Server is also server-side computing, the benefits that come with server-based setups (e.g. centralized management, better security, remote administration, etc) also apply.

Deploying applications and performing patches on VDI and Terminal Server platforms are also much faster because everything is done centrally. Again, this reduces downtime and increases productivity.

High ratio of users/server

Terminal servers are very capable of handling a few hundred to several thousands of users. And this has been proven time and time again in its over 13 years of existence. So if you have a lot of users that need to perform simple, repetitive tasks in front of a computer, then this is the DV platform for you.

Eyes only security

It’s easy to implement eyes-only security. That means, users can only view things on the screen but they won’t be able to copy or paste. You can also prevent them from doing other tasks like printing.

Highly managed

This allows users working on different shifts to share the same computer and access their data from different computers. Of course, they’ll have to be assigned unique login details. But there’s a downside to the feature that enables this capability.

A terminal server is highly manageable because multiple users connect to a single terminal server and are only differentiated through individualized sessions. But while this greatly reduces the number of administrative tasks per user, it also allows a single point of failure for a large number of users.

If there are 400 users connected to one terminal server and that terminal server goes down, all 400 users will be affected. Yes, you can later on connect those users to other terminal servers but still, that single event would have already inconvenienced a large number of users and caused widespread disruption. So even if terminal servers are great for admins, they don’t suit well with end users.

Client Hypervisors – Type 1 and Type 2

client hypervisors

A client hypervisor is similar to those hypervisors you run on servers in that it can support multiple VMs on top of it. But as the name implies, this kind of hypervisor is installed on a client device and not on a server. That means, it doesn’t have to be online all the time.

Unlike the two desktop virtualization platforms we mentioned earlier, client hypervisor makes use of client-side computing. Hence, you can take full advantage of computing resources you may have on your device, like large CPU and RAM. That is why client hypervisors are ideal if your end users need better graphics or computing power.

There are actually two types of client hypervisors. And because they have their own distinct advantages and disadvantages, we’d like to tackle them separately. The main difference is that, in a Type 1 client hypervisor, the hypervisor is installed on bare metal, i.e. on the hardware itself. Type 2, on the other hand, is installed on an operating system.

Type 1 client hypervisors

Option to create a single Windows image or multiple VMs

Once you’ve installed a Type 1 client hypervisor software on say a laptop, you can then create virtual machines and run them on top of the hypervisor. That means, you can use a single Windows image and distribute it to the different laptops and desktops in your organization.

Alternatively, you can have multiple virtual machines. So for instance, you can create an “office VM”, which your employee is supposed to use when at work, and a “home VM”, which he can use when at home. The working environment inside the “office VM” may have certain restrictions, while the one in the “home VM” may offer more freedom.

Perfect for BYOC

Client hypervisors are ideal for BYOC arrangements. Your team members can buy whatever laptop they like (assuming of course it can support your hypervisor) and you simply install the hypervisor and the necessary VMs on them. Because this “installation” is considerably quicker than regular software installations, this will save a significant amount of time when compared to the usual way of installing the operating system and all necessary applications.

Even if a computer breaks down, you can easily bring them back into operation in no time (see succeeding section).

Shorter downtimes

One advantage of working with virtual machines is that you can reimage them.

This basically entails creating a duplicate copy of a VM. When your system starts slowing down after a year or a few months, you can simply copy and paste that duplicate VM. You won’t have to install or configure anything and can practically be back up and running in just a few minutes.

Best of all, your system will be able to run like a freshly installed operating system. Similarly, if an employee’s laptop bogs down, you can simply find an available laptop, copy the VM from the first laptop to the second, and he can get back to work in just a few minutes.

In addition, there are ways to update an OS by synchronizing the VM with a data center. So updates can be performed much faster as well.


Type 2 client hypervisors

As mentioned earlier, a Type 2 client hypervisor differs from its Type 1 sibling simply by the manner it is installed. While the latter is installed right on top of bare metal, the former has to be installed on top of an operating system. All other features, like the ability to: support multiple VMs, run locally on the device, and enable quick recovery when something goes wrong are the same … well, almost.

It’s also one way to continue using an older OS version on top of a newer one. For instance, this is the technology used in Windows Virtual PC, which enables users to shift to Windows XP Mode while on Windows 7.

Again, Type 2 has some of the benefits of Type 1. However, there’s one major problem. Because the VMs (on the hypervisor) have to be installed on an underlying OS, you now have to manage more desktops – the underlying OS and all the VMs running on top of it. That’s going to make things more complicated. If you need to perform patches, upgrades, or antivirus-related tasks, you’ll have to do it on all those desktops.

Taking this into consideration, then Type 1 client hypervisors are definitely better than Type 2. So if we end up mentioning more strong points of client hypervisors later in the text, you can be sure we’re referring to Type 1 hypervisors.

Application Virtualization

application virtualization

Application virtualization allows you to virtualize an application, thereby encapsulating all files needed to run the application, including DLLs, registries, etc., into a single file. You can then run that single file on an operating system without installing it there.

Saves storage space and time

Because the virtualized application isn’t installed on the operating system, it doesn’t occupy disk space. Furthermore, in technologies like Citrix XenApp, the application is streamed from a central location to devices that need it. Thus, if you have thousands of devices needing the application, you will be able to save a significant amount of time because no installation is involved during deployment.

Centralized management

In the scenario given earlier, wherein the virtualized application is streamed from a central location, you again enjoy the benefits of a server-based setup – i.e., centralized management, better security, and so on.

Supports aging or conflicting applications

One of the real sweet spots of application virtualization is its ability to prolong the life span of legacy applications. So if you have an aging and highly customized application that you don’t want to part with but haven’t had any luck in making it run on the operating system your company is migrating to, then you can still find hope in application virtualization.

This kind of desktop virtualization is also ideal for problematic applications, i.e., those that always have conflicts with other apps on your device. By virtualizing those problematic applications you can isolate them from the rest and let everything run smoothly.

Remember though that not all applications can be virtualized. So there can be exceptions.


At this point, you’re now ready for Part III. There, we’ll zoom in to the challenges faced by desktop virtualization, its operational benefits (where its strength really lies), and some tips and best practices to make the most out of a DV investment. We’ll then end that part with a glimpse at one of the best desktop virtualization products in the market today.

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