Administration

Configuring Load Balancing for RDS Hosts
By default, View Connection Server uses the current session count and limit to balance the placement of
new application sessions on RDS hosts. You can override this default behavior and control the placement of
new application sessions by writing and configuring load balancing scripts.
A load balancing script returns a load value. The load value can be based on any host metric, such as CPU
utilization or memory utilization. View Agent maps the load value to a load preference, and reports the load
preference to View Connection Server. View Connection Server uses reported load preferences to determine
where to place new application sessions.
You can write your own load balancing scripts, or you can use one of the sample load balancing scripts
provided with View Agent.
Configuring load balancing scripts involves enabling the VMware Horizon View Script Host service and
setting a registry key on each RDS host in a farm.
Load Values and Mapped Load Preferences
View Agent maps the load value that a load balancing script returns to a load preference. View Connection
server uses reported load preferences to determine where to place new application sessions.
The following table lists the valid load values that a load balancing script can return and describes the
associated load preferences.
Table 9‑2. Valid Load Values and Mapped Load Preferences
Valid Load Value
Load Preference
Reported by View Agent Description
0 BLOCK Do not choose this RDS host.
1 LOW Low preference/high load.
2 MED Medium preference/normal load.
3 HIGH High preference/light load.
Load Balancing Feature Constraints
The RDS host load balancing feature has certain constraints.
n
Anti-infinity rules can prevent an application from being placed on an RDS host, regardless of the
reported load preference. For more information, see “Configure an Anti-Affinity Rule for an
Application Pool,” on page 170.
n
Load balancing affects new application sessions only. An RDS host that contains sessions in which a
user has previously run an application is always reused for the same application. This behavior
overrides reported load preferences and anti-affinity rules.
n
Applications are launched on an RDS host where a user already has an existing session, even if the RDS
host reports a BLOCK load preference.
n
RDS session limits prevent application sessions from being created, regardless of the reported load
preference.
Chapter 9 Managing Application Pools, Farms, and RDS Hosts
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