Back in May 2010, I started my Top 10 Mistakes Made with Virtual Desktops. I talked about how much bandwidth certain activities require when using XenDesktop and HDX. The table I provided is great, but it does pose the question, “What does a person do with this information?” Since then, I’ve been able to spend more time and have recently completed the bandwidth planning guide, which you can get by accessing the XenDesktop Design Handbook. But let’s take a closer look at what the planning guide says…
First, we have a list of bandwidth requirements for certain activities (Office work, Internet activities, Flash rendering, WMV videos, etc). I can simply use the following formula to create my average bandwidth consumption:
The formula works great, BUT it is an average for 1 user. The whole concept of averages is that most of your users will be doing activities that require smaller amounts of bandwidth while a few will consume more. By averaging them all out, we create a buffer. Let me show you what I mean. First, think of a single user’s day and calculate how much time they spend doing certain activities:
- Office-based: 4 hours
- Internet: 1 hour
- Printing: 15 minutes
- Flash Video: 30 minutes
- Standard WMV Video: 10 minutes
- HD WMV Video: 5 minutes
- Idle: 3 hours (one hour lunch and two, one hour meetings)
If I use this scenario, the user will require and average of 78Kbps of bandwidth, (43kbps or less for low end and 1812 kbps for high end). If I average this out across hundreds of users within a site, I have a small safety net for those few users who are watching videos. Unfortunately, because the difference between low usage and high usage is so great, very few users can simulatanously consume high levels of bandwidth before the experience fails.
Hopefully, I’ve explained the dangers of using averages, but that begs the question of how to plan bandwidth requirements.
- Start with the averages. That is your baseline.
- Define a burst level of required bandwidth. Chances are high that not all users will be watching HD WMV video at the same time. So by creating a 20% safety net (just an example, your safety net will differ) on top of our average bandwidth calculation, we should be able to provide users with acceptable performance, even when watching videos.
Hopefully, this sheds some light onto planning your XenDesktop environment.
Don’t forget to get this planning guide and many others in the XenDesktop Design Handbook.
Daniel – Lead Architect