Shortly after making the upgrade we noticed that our Citrix servers became unresponsive at random times throughout the day: you could ping them, but that's about it. Any attempt to RDP or log in even at the console level was an absolute failure. If you are experiencing this problem, I would recommend upgrading your servers to Server 2008 R2 SP1, and applying the following Microsoft Hotfix: KB 2465772. In addition, you're going to want to install at LEAST this Citrix Hotix as well: CTX127023. But really, I would install as many Public Hotfixes for XenApp 6.0 as possible that apply to your environment.
If that would have been the end of the freezing saga, I would have been content. However, the freezing dragon decided to rear its ugly head again: whenever we tried to shut down a Citrix server after having a decent amount of load on it, it froze. Basically, it would sit on the Windows "Shutting down..." screen with the spinning circle to never fully shut down or recover without a hard power off.
After working with Microsoft and Citrix, it turns out that there is a Citrix Hotfix that's working its way toward becoming public (supported by Citrix), that should be available in the coming weeks. If you are experiencing this same issue (freezing when shutting down) you're going to want to keep your eye out for Hotfix 46 (full name: XA600W2K8R2X64046).
UPDATE: I've added a new post that provides links to this hotfix.
In the meantime, there are a couple pages you should be keeping an eye on:
- The list of Public Hotfixes currently available for XenApp 6.0
- A list of recommended Microsoft Citrix Hotfixes for XenApp 6.0 and Server 2008 R2
Both of these get updated from time to time, so you'll want to bookmark them and see what's new whenever you get a chance.
As always, this is what worked for me, in our environment, so your mileage may vary and I won't be responsible for any problems this post may cause :)