About Power Management and Load Balancing for Farms in Horizon Cloud

This topic describes how Agent Load Index, based on load balancing settings, is used for power management in RDSH farms in Horizon Cloud.

For more information about any of the settings mentioned in this documentation article, go to First-Gen Horizon Cloud Pods - Creating and Managing Farms and locate the setting within that article.

Horizon Cloud agents use five settings (CPU Usage Threshold, Memory Usage Threshold, Disk Queue Length Threshold, Disk Read Latency Threshold, and Disk Write Latency Threshold) to calculate the Agent Load Index, a value between 0 and 100 that measures each VM's load.

Important: Because of the key role that Agent Load Index plays in power management, it is essential that you select appropriate values for these settings so you can achieve the desired balance of power consumption and performance in your environment.

System's Determination of Farm Usage

The system determines the usage of a specific farm by selecting the higher of the following two percentage values:

• Session occupancy

  The number of active sessions within the farm divided by the total number of sessions possible on the powered-on VMs in the farm. The number of sessions possible is calculated by multiplying the number of powered-on VMs in the farm by the Sessions per VM value you set for the farm.

• Average load index

  The average Agent Load Index of the powered-on VMs in the farm.

For farm expansion, the system then compares the selected value to the high threshold for the Power Management setting you selected for the farm.

In both of the following examples, the Power Management setting for the farm is Optimized Performance. The high threshold for the Optimized Performance setting is 50%, meaning that when the usage reaches 50%, the system powers up one of the unused VMs.

Note: In the examples below, the Max VMs setting for the farm must be greater than 1. Otherwise, the expansion does not occur.

Example - Farm Expansion Due to Session Occupancy Exceeding the High Threshold

In this example, settings are as follows:

• Sessions per VM = 20
• High threshold for Power Management = 50%

Example - Farm Expansion Due to Average Load Index Exceeding the High Threshold

In this example, settings are as follows:

• Sessions per VM = 20
• High threshold for Power Management = 50%