We are so excited to VDI, we often forget to take a step back and focus on what we are trying to do . Here is a recent example ...
We must find a way to get an application for our users. Our first problem is that many of our users are not local, which makes the installation of 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 heard that VDI can help us. 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 not blame the person for VDI already believe is the correct answer because the marketing teams that are focused on VDI did a great job blanketing us with VDI message. And unless you are knowledgeable about the functionality with different products, you might miss the nuances and buy something you did not expect.
If I were to make a recommendation with this particular client, I refer them to XenDesktop 7 App Edition (for those of us who have been around for a while, I refer to XenApp), which provides essentially an application to a user instead of the entire desktop. This solution closely matches what the user needs.
But what does it for 500 users? Not much ... just three physical servers with two Intel Xeon E5-260 @ 2.9GHz with 192GB of RAM.
Of course, many will think that this is all theoretical. But to prove it's not just fairy tales and unicorns, we have built, tested and validated this design guide for mobilizing Windows applications in the Citrix Solutions Lab (I'll give more gory detail 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 plan to better understand the architecture 5-layer).
This solution gives you the following:
- delivery of almost all Windows applications to any end point in any location without requiring the application to be rewritten to the many types of types of end devices and form factors.
- The traffic is protected in SSL because it crosses the public network connections with NetScaler Gateway
- An environment capable of supporting 500 concurrent users, with only 21 virtual servers (Note that VDI would require more 500 virtual machines).
- more importantly, the whole environment uses for local storage . There is nothing special about the local storage that each physical server includes (8) 300GB SAS drives running at 15000 RPM configured with RAID 10
Of course, this is just conceptual, then what the physical architecture look like?
- 3 physical servers required to support 500 users, each with RDS host supporting about 50 users. If multiple users are needed, another server is added like the config "Server 3". We do not have to worry about scaling access components and layer control for a while because they have low utilization.
- Three different VLANs DMZ, VM, and management traffic. I know some of you remember the risk with putting the NetScaler VPX Gateway on internal servers and having the VLAN for VM go to the DMZ. Depending on the size and complexity of your infrastructure, this could be a non-issue as long as you have the appropriate 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 support 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, see the Design Guide for mobilizing windows applications
Daniel - Lead Architect
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