We get so excited with the thought of VDI, we often forget to take a step back and focus on what we are trying to do. Here is a recent example…

We need to find a way to get an application to our users. Our first problem is that many of our users are not local, which makes installation a challenge. The second problem is that many users want to use the application on non-traditional devices (tablets) because it is more convenient. We’ve heard that VDI can help us with this. What will it take?

First, this is a good question, but unfortunately, the person has already decided on a solution without understanding what is possible. I can’t blame the person for already believing that VDI is the right answer because the marketing teams that are focused on VDI have done a great job blanketing us with the VDI message. And unless you are knowledgeable about the functionality with different products, you might miss the nuances and buy something you weren’t expecting.

If I were to make a recommendation with this particular customer, I would steer them to XenDesktop 7 App Edition (for those of us who have been around for some time, I’m referring to XenApp), which basically delivers an application to a user instead of the entire desktop. This solution aligns closely with what the user needs.

But what will it take for 500 users? Not much… just three physical servers using two Intel Xeon E5-2690 @2.9GHz with 192 GB of RAM.

Of course many will think this is all theoretical. But to prove this isn’t simply fairytales and unicorns, we built, tested and validated this Design guide to mobilize windows apps in the Citrix Solutions Lab (I will provide more gory details in a future blog).

When we go through the numbers and incorporate it into our 5-layer conceptual model, we get the following (Read about the XenDesktop 7 blueprint to better understand the 5-layer architecture).

This solution gets you the following:

  1. Delivery of almost any Windows-based application to any endpoint to any location without requiring the application to be rewritten for the numerous types of endpoint device types and form factors.
  2. Traffic is protected within SSL as it crosses over public network connections with NetScaler Gateway
  3. An environment, capable of supporting 500 concurrent users, with only 21 virtual servers (Note that VDI would require over 500 virtual machines).
  4. Most importantly, the entire environment is using standard local storage. There is nothing special about the local storage as each physical server includes (8) 300GB SAS drives spinning at 15,000 RPMs configured with RAID 10.

Of course this is just conceptual, so what does the physical architecture look like?

  • 3 physical servers required to support 500 users, with each RDS host supporting roughly 50 users. If more users are required, another server is added resembling the “Server 3” config. We don’t have to worry about scaling the Access and Control layer components for some time as they have low utilization.
  • Three different VLANs for DMZ, VM, and Management traffic. I know some of you will point out the risk with putting the NetScaler Gateway VPX on internal servers and having the VLAN for that VM go to the DMZ. Depending on the size and complexity of your infrastructure, this might be a non-issue as long as you have the proper configuration and lockdown procedures.
  • Access Layer and Control Layer configured with N+1 availability in that if one component fails, a secondary component is available to take over the load.

When trying to decide what to do in your own environment, remember to look before you leap.

If you want to read the entire design, check out the Design guide to mobilize windows apps

Daniel – Lead Architect