Citrix XenApp Load Balancing Information

The Citrix XenApp Slow Start Load Balancing feature of XenApp 4 and onwards works on the following formula by default.

Current Res Load += Max_Load - Current Res Load /2

This means the load evaulator would like the following.

1 Logon 0 + (10000 - 0 / 2) = 5000
2 Logon 5 + (10000 - 5 /2) = 7500
3 Logon 7500 + (10000 - 7500 /2 ) = 8625
4 Logon 8625 + (10000 - 8625 /2 ) = 9312
5 Logon 9312 + (10000 - 9312 / 2) = 9656
6 Logon 9656 + (10000 - 9656 /2) = 9828
7 Logon 9828 + (10000 - 9828 /2) = 9914
8 Logon 9914 + (10000 - 9914 /2) = 9957

Remember 10,000 is fully loaded

This means the ramp up of load occurs quite quickly. The idea being that after a few logons the server should be loaded to somewhere above the farm average and the next request will goto another server in the pool.

Once a logon has completed the Load is recalculated to reduce the Load Value.

The divide by 2 is the default and can be changed if you wish to allow more logons to the server without reporting such a high load. This can be changed with the following registry key.
HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\IMA\LMS\ILBMultiplier