Desktops and servers are different beasts
The first lesson is a tough one: Chuck your past. Desktops and servers are different beasts and attempting to compare the two is an exercise in futility. Both have vastly different performance characteristics and needs. Most importantly, never forget this key fact: While you might be able to “bury” a performance issue with a virtual server while you order more resources to cover it, that won’t happen with a virtual desktop. A user’s desktop, though, is front and center all day long. There won’t be any such thing as a “blip” that you can ignore.
VDI requires thinking about infrastructure resources a bit differently
In virtualizing servers, you’re almost always going to run out of RAM before you exhaust processor and disk resources. With VDI, you’re more likely to run out of disk resources before anything else. In particular, you will more quickly hit a disk performance wall than you will a storage capacity limit. Again, storage performance has always been important even in server virtualization, but the visibility is increased in a VDI scenario in which boot storms can take place when masses of users boot their workstations simultaneously.
So, my advice: Don’t believe that your experiences with server virtualization will have fully prepared you for desktop virtualization. Make sure that your team has done its homework so that you don’t roll out a service that lands with a thud.
Licensing can be a bear
If you’ve done much in the way of server virtualization, you’ve had to learn about new ways to license your software and have had to look through the fine print in the software contracts that govern your server-based software to ensure that a virtual deployment fit the rules. Guess what? It only gets worse when you go to VDI. First, you have to worry about things like Microsoft’s VDA licensing. Moreover, you have to work with individual software vendors to make sure you can deploy client software via virtual desktops. For some inexplicable reason, some software vendors get pretty greedy when it comes to new ways to provision software, even when you have concurrent usage licenses (yes, I’m bitter!).
Advice: Never assume that any of your license agreements allow you to provision software via a virtual desktop.
WAN connectivity becomes more critical
If you’re deploying virtual desktops for internal consumption only, WAN bandwidth may not be a big deal. However, as users start to consume virtual desktops from outside the firewall, appropriate bandwidth needs to be secured in order to make sure that users have a good experience.
You’re not going to save money up front
Now, for the worst news… you’re not going to save money up front by going to VDI. At best, you’ll break even and will probably have to spend a bit more to do it right. Over time, you may see some operational savings as you extend desktop equipment life cycle replacement and reduce power costs, but don’t believe the “huge ROI” hype. There is simply too much infrastructure that needs to be purchased to do it right.
That said, there may still be great reasons to do VDI, but your justification will have to be non-financial outcomes-based rather than having a direct ROI.
VDI has the potential to transform the way that you manage the desktop, but there are some realities that need to be faced before you take the plunge. Make sure you implement for the right reasons, though. Perhaps you need to provide desktops to remote workers or maybe you want to create an on-demand virtual computer lab for your students. Both are worthy goals, but check your expectations before you move forward.
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