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 Horizon Cloud Pods - Create a Farm 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%
Before Expansion After Expansion
Powered-on VMs
VM 1
  • Sessions running = 10
  • Agent Load Index = 25%
Usage values
  • Session occupancy = 10 sessions running / (20 Sessions per VM x 1 VM) = 50%
  • Average load index = Agent Load Index 25% / 1 VM = 25%

The higher of the two values is 50%, which matches the high threshold for the Optimum Performance setting for Power Management. As a result, the system powers on a second VM.

Powered-on VMs
VM 1
  • Sessions running = 10
  • Agent Load Index = 25%
VM 2
  • Sessions running = 0
  • Agent Load Index = 0%
Usage values
  • Session occupancy = (Sessions running 10 + 0) / (20 Sessions per VM x 2 VM) = 25%
  • Average load index = (Agent Load Index 25% + 0%) / 2 VMs = 12.5%

The higher of the two values is 25%, which is below the high threshold for the Optimum Performance setting for Power Management. As a result, the system takes no action.

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%
Before Expansion After Expansion
Powered-on VMs
VM 1
  • Sessions running = 5
  • Agent Load Index = 50%
Usage values
  • Session occupancy = 5 sessions running / (20 Sessions per VM x 1 VM) = 25%
  • Average load index = Agent Load Index 50% / 1 VM = 50%

The higher of the two values is 50%, which matches the high threshold for the Optimum Performance setting for Power Management. As a result, the system powers on a second VM.

Powered-on VMs
VM 1
  • Sessions running = 5
  • Agent Load Index = 50%
VM 2
  • Sessions running = 0
  • Agent Load Index = 0%
Usage values
  • Session occupancy = (Sessions running 5 + 0) / (20 Sessions per VM x 2 VMs) = 12.5%
  • Average load index = (Agent Load Index 50% + 0%) / 2 VMs = 25%

The higher of the two values is 25%, which is below the high threshold for the Optimum Performance setting for Power Management. As a result, the system takes no action.