Enterprises that manage multiple locations, particularly smaller branch offices, can benefit from Virtual Desktop Infrastructure (VDI). Branch office servers can be eliminated, desktop troubleshooting reduced, and administrative burden lowered. It’s not a panacea, and IT management should understand the limitations, but for many it will be an excellent option to provide virtual desktops to branch office staff.

VDI 101

VDI expands the concept of server virtualization to desktops. The notion is that PC hardware if often under-utilized and by deploying many virtual desktops on a single server resources can be more fully utilized. Many virtual desktops can typically be deployed on a single server residing in the data center.

Virtual desktops on a central server are accessed using Remote Desktop Protocol (RDP). A PC or thin client device establishes a connection with the VDI server and the RDP session presents an individualized desktop to the user over the RDP connection. The virtual desktop is centrally managed, and the only hardware to manage is the VDI server in the data center. Assume 10 virtual desktops can be housed in one mid-range server (dependent of CPU, RAM and storage capacity), and it becomes clear how administrative burden can be significantly reduced. Figure 1 illustrates a simplified VMware remote VDI implementation.

Figure 1. Basic VDI Configuration with VDM

Source: Adapted from VMworld 2007 Presentation DV18, Slide 41

The Benefits

VDI offers many benefits to remote office user, including:

• Security. Connectivity can and should be secured with SSL encryption. Whether through an SSL VPN or a SSL enabled connection broker, the connection between the desktop and the VDI server must be secured. The entire desktop is managed as a virtual instance on a server in the data center, meaning IT has full and easy control over anti-malware software, OS patching, and network access. In the unlikely event that a virtual desktop becomes infected with malware, the virtual instance can be deleted and replaced with a clean image in minutes.
• User experience. The user experience is identical to having an individualized desktop and application set. In most cases the user wouldn’t even know they were using a virtual desktop, as long as adequate WAN connectivity is in place.
• Simplified branch management. The branch office servers get retired with VDI. No more domain controllers, file or application servers – and the accompanying administrative overhead – at the branches.

The Drawbacks

VDI is not for everyone. Prior to taking the leap into VDI, consider the following:

• Bandwidth. When deploying VDI at branch offices it is important to size bandwidth appropriately. The bandwidth requirement for a typical VDI/RDP stream isn’t excessive, but it is important to size the implementation properly. Expect to utilize about 125kbps of reliable WAN bandwidth per VDI session.
• Certain applications don’t work well. Streaming audio or video will not work well using VDI unless some tweaking is done to offload the audio and video processing to the RDP client. This may not be important to some, but to those involved in distance learning using audio and video, or for enterprise video streaming it’s something to bear in mind. It’s not an insurmountable issue, but it should be considered.
• Significant planning and design is required. It will not suffice to simply define a virtual desktop to server ratio, provide some bandwidth, and implement the solution. It will almost certainly be necessary to thoroughly test many scenarios and properly design the solution prior to implementing.

Recommendations

VDI moves much of the infrastructure requirement and administrative burden from the branch office to the head office or data center. The solution represents a significant opportunity to many multi-site enterprises, but not all will reap the rewards. Consider the following prior to making an investment:

1. Make sure enough server horsepower is in place. When creating virtual desktops options abound, depending on the requirements of the branch office users. Ensure VDI servers are in place to shoulder the load of the necessary virtual desktops.
2. Do some bandwidth tests. It’s not just bandwidth, it’s also necessary to consider WAN/Internet connectivity performance. High latency, packet loss, and jitter on WAN connections can also be deal breakers.
3. A pilot is a must. This is another situation where a pilot is absolutely essential. Trial a solution with a couple of servers in the data center and a couple of branch offices. As always, carefully consider user feedback before rolling out a solution.

Bottom Line

Virtual Desktop Infrastructure (VDI) has the potential of making branch office computing much easier to manage. Multi-site enterprises stand to significantly reduce the branch office IT administrative burden by centralizing virtual desktops in the data center. Take a serious look at VDI if IT administration for branch offices has become overly cumbersome.