Ten Important things to consider when troubleshooting Load Balancing Issues in XenApp 6.0 and 6.5
1. Why are you troubleshooting Load Balancing? Keep in mind Load Balancing is turned on by Default in XenApp so if you don’t configure Load Balancing, you really don’t need to troubleshoot it at all!
2. Each user that accesses a XenApp server checks out one license and puts a load of 100. If 100 users connect to a XenApp server you will achieve the maximum load of 10000. At that point the server will stop taking new connections
3. If you reboot your server, you will notice the load will be 10000. In this case the reason is: Not all XenApp services have started and the server is not ready to take any connections so it puts itself in a full load mode preventing any connections. Once all services have started then the XA server will drop the load to 0 and will start takeing new connections
4. The Xenapp computer in charge of managing the load of the farm is the ZDC (Zone Data Collector). The ZDC keeps track of all dynamic information for the farm . Server load is a dynamic piece of data (users log in and out all the time) therefore it is managed by the ZDC
5. So, if you troubleshoot any Load Balancing issues remember to check your ZDC. If you notice discrepancies you can change your ZDC in the farm and see if the load stabilizes
6. If one server is getting a load much higher or lower than the other servers in the farm, a good troubleshooting step is to remove the server out of the farm and rejoin it back. This will reset the settings of the server on the farm and can resolve a nuisence
7. Also creating a worker group with only a trouble server and assigning a load balancing policy to it, rebooting the server and then removing the load balancing policy might help resolve a issue
8. If Load balancing policies are applied to a farm, disabling a policy is always a good troubleshooting step
9. Always check for Load Balancing related hotfixes at the Citrix.com site. Worker Groups and Load Balancing Policies are always good candidates for hotfixes in the XenApp environment
10. Understand the difference between Load Evaluator and Load Balancing:
Also, keep in mind:Load Balancing Policies are used to specify which group of servers should be used to start Citrix/ICA sessions whereas Load Evaluators are used to divide the number of users equally over the number of servers available, based on user load (100 users = full load by default) and/or used resources such as CPU Utilization Load, Memory Usage, Page Swaps, and Load Throttling.