Virtual desktop design – The right approach

One of the first questions someone doing desktop virtualization wants answered is usually one of the following questions

  • How many servers do I need?
  • How many IOPS?
  • How many XenDesktop Controllers do I need?

I’ve seen it many times and have been asked these questions many times. The typical answer is “It depends” (I really hate this answer BTW). The wrong answer is any number (You don’t have enough information). A more accurate answer is “Let’s solve for X, where X is the number of servers” (Pretty much the same thing as “It depends”, but we didn’t have to say “It depends”.)

So in order to start solving for X, we need to ask a wide range of questions around the user’s usage requirements, location, personalization, hypervisor, hardware specifications, etc. The list can be quite long if you want a realistic and accurate answer. The problem with this approach, which is the same approach I’ve seen many people take, is that


The number of servers, number of IOPS, number of XenDesktop controllers are some of the LAST design decisions you should answer. Before you can answer this, you need to understand the user’s endpoints, you need to figure out how the users will access the environment and you need to understand what form user’s virtual desktop will take.

The right way to do a virtual desktop design is to follow the 5-layer model:

  1. User Layer: Focus on the decisions that impact the users directly: endpoints, receiver, etc. Should be done for each user group.
  2. Access Layer: What types of authentication, encryption and bandwidth does each user group require? Should be done for each user group.
  3. Desktop Layer: What does the user’s virtual desktop look like? OS, Apps, profiles, policies, printing, etc. Should be done for each user group.
  4. Control Layer: What and how many infrastructure components are required (Access Gateway, StoreFront, XenDesktop/XenApp controllers, Provisioning Servers, etc). Should be done for each data center.
  5. Hardware Layer: How much physical hardware is required, which includes number of servers, total storage space requirements, total IOPS requirements, number of virtual machines, etc. Should be done for each data center.

When you use Project Accelerator, you see this 5-layer model depicted in the architecture diagram.

When you look at the NEWLY updated Virtual Desktop Handbook, you see the design phase following the same flow as well as many of the different design decisions you should answer.

I encourage you to take a look at both. And notice that the latest additions to the Virtual Desktop Handbook go into more details for many of the appropriate design decisions within these layers.

Stay tuned for more, as we are working on additional updates to the handbook.

Daniel – Lead Architect

Project Accelerator
Citrix Virtual Desktop Handbook

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