How many Citrix vusers can I run on each agent?
For all Windows versions other than Windows 2003, it is recommended that a maximum of 50 users be run on a single agent machine. It is not possible to scale virtual users based on machine specifications due to a Windows GDI limitation. GDI is the Graphical Device Interface in Windows. When Silk Performer simulates virtual users every virtual user consumes GDI resources. Tests show that the GDI limit allows us to run 50 users on a box without issue. In order to run large loadtests additional agents are required rather than more powerful agents. For Windows 2003 machines additional virtual users can be run, this is possible due to Windows 2003 having an enhanced system resource management.
Note: if Terminal Server is installed on the agents it severely reduces the number of users that can run on the agent (approx by a factor of 10) and it is recommended that Terminal Server is not installed on the agent machines.