Virtualization: The benefits of VDI

Using virtual desktop infrastructure can give you a degree of flexibility and ease of management using limited resources.

Jorge Orchilles

Adapted from “Microsoft Windows 7 Administrator’s Reference” (Syngress, an imprint of Elsevier)

Virtual desktop infrastructure (VDI) is an alternative desktop deployment model for Windows 7. Using VDI can help save time and money, provide greater defense against catastrophic failure, improve update speeds, and provide an easy way to customize desktops for certain users or groups of users. You should consider deploying VDI when desktop flexibility is more important than immediate cost savings.

Instead of running a local copy on each user’s desktop, you create a common image and store it on one or more servers in the datacenter. A hypervisor then deploys the image to a server. A hypervisor is a layer of software that lets you run several OSes simultaneously on a common computer while maintaining isolation between the different OSes. Hyper-V is the Windows Server hypervisor.

There are several major benefits to implementing VDI:

  • You can rapidly deploy a common, supported desktop environment across your network. Create a single Windows 7 desktop image and use that image to deploy virtual machines (VMs) on your server hypervisor. A single server can support many virtual desktops. Each of these desktops reacts as a standalone Windows 7 desktop. Unlike using Remote Desktop Services (RDS), the users connecting to a virtual desktop can have full access to all features of that VM without impacting the other virtual desktops or the host server. Your users could still use the Remote Desktop Client to connect to their virtual desktop.
  • You can centrally deploy updates and changes to Windows 7. Simply update the Windows 7 desktop image and redeploy that updated image to all your users. The next time they log on, they’ll have the updated image with all their settings maintained.
  • If there’s a problem with an update that requires you to roll back to a previous stable version of the desktop image, you can do so quickly. Save a copy of the previous image before performing the update. This will help you roll back by redeploying the previous image. Then have your users log off and log back on to receive the previous image. Laptops, desktops and the clients all connect to a VM running Windows 7 in the datacenter.

Potential barriers

There are some barriers to implementing VDI. The start-up costs can be high, and the return on investment takes longer than it does on a server virtualization project. This is a business decision you should not take lightly. You need to plan and budget before embarking on the project. Consider the following specific areas:

  • VDI may not reduce desktop costs because any savings are typically redirected into server, network and storage infrastructure. You’ll have to make some improvements in your desktop management and user management to effectively support large numbers of virtual desktops. Applying Group Policy through Active Directory to redirect user folders and implementing roaming profiles will increase the flexibility of your VDI design.
  • A user connected to a virtual desktop requires a constant connection to the network. Whether this is through a LAN or across a wide area network (WAN) or a remote connection, the user must be connected to the virtual desktop to be productive. Your user community must also be able to operate in a disconnected environment, or VDI won’t be a suitable solution. If you don’t have many mobile users, or if they only work when they’re connected to the network, then this could be a viable solution.
  • Planning your VDI deployment is critical to the success of the project because it can be a complex process. It’s also a potentially significant investment in infrastructure. Defining which users will benefit the most and what virtualization components you’ll need to deploy is crucial for success.

Distributed virtual desktops

A distributed desktop model lets you deploy different desktop images to a specific group of users based on their location or job function. This type of model can be useful if you have a number of different types of users in a single location or users in a variety of locations, such as branch offices.

Each group has different desktop requirements or is connected by a slow or intermittent link. The remote users may have a file server that stores their files and information.

The pre-boot execution environment (PXE) is another distributed desktop design. This method lets you deploy an image to a server and a desktop to download and boot that image at startup. You can develop and deploy several desktop images and have them assigned to a certain desktop or group of desktops. When the user starts that desktop, the image is streamed to the device as it starts up. Changing a desktop image is as simple as reconfiguring the device’s target image and restarting the desktop.

This is a viable design if you have to run applications from the local desktop. Some applications require a hardware key or a specific MAC address for licensing. Applications that require special graphics or additional cards or adapters not supported in a virtual environment are also good candidates for this type of deployment.

The drawbacks and benefits are as follows:

  • You have to load the individual images with any applications or drivers required for the individual desktop computers. Unless all the desktops are identical, you may need to add different drivers required for each type of hardware for which the image is being prepared.
  • You can configure a different image to load on a desktop as a shift changes or new updates are configured. This is particularly useful because a new image is loaded each time the desktop is rebooted. Viruses and malware are limited in their effectiveness because the entire desktop image is reloaded each time the desktop is reloaded.
  • The VDI image is received from the primary datacenter. The management station controls which images are assigned to the local and remote users. Local users connect to the image assigned to them from the VDI server in the datacenter.
  • This model is best used with a local server that holds the desktop images. Loading a desktop image over a WAN is a slow process that will discourage remote users from rebooting their desktops. In this scenario, you should look at using either a local VDI or a distributed VDI solution.

You can also opt to distribute desktops with something like Microsoft System Center Configuration Manager (SCCM). You can use this to distribute both applications and desktops to users’ desktops, both local and remote. This model will actually install the desktop OS on the targeted desktop.

Whichever model you choose, you’ll have to plan and test your solution for optimum success. You can also use SCCM in conjunction with another System Center component, System Center Virtual Machine Manager 2008, to create, deploy and manage desktops in a distributed environment.

When it comes to deploying a user’s desktop, there are several options and one design rarely fits all situations. You can see from these different scenarios that you can use a combination of all available options to meet your specific needs.

Jorge Orchilles

Jorge Orchilles began his networking career as a network administrator for the small private school he attended. He’s currently a security operating center analyst, and recently completed his Master of Science degree in management information systems at Florida International University.

©2011 Elsevier Inc. All rights reserved. Printed with permission from Syngress, an imprint of Elsevier. Copyright 2011. “Microsoft Windows 7 Administrator’s Reference” by Jorge Orchilles. For more information on this title and other similar books, please visit