The Azure Virtual Desktop Autoscale feature (which evolved from the "Start/Stop VMs during off-hours" solution) can use performance metrics, such as CPU utilization, to make scaling decisions. To enable this functionality, performance counters from the session host virtual machines must be collected and sent to a Log Analytics workspace. This is achieved by configuring the Diagnostic settings for the session hosts. These settings enable the collection of guest-level performance data and route it to the specified Log Analytics workspace, making it available for the Autoscale scaling plan to evaluate against the defined thresholds.

A. Enable change tracking: Change Tracking and Inventory is an Azure Automation feature used for tracking configuration changes within VMs, not for collecting performance metrics for scaling.
B. Configure the Power Management settings: These are guest operating system settings that control sleep or hibernate states. AVD Autoscale manages the VM power state (deallocated) from the Azure control plane, not from within the guest OS.
D. Install the Azure Virtual Desktop Agent: The AVD Agent is required for a VM to function as a session host, but it does not collect or forward the performance counter data needed for Autoscale. This data collection is a separate monitoring configuration.

1. Microsoft Documentation - Autoscale scaling plans and example scenarios in Azure Virtual Desktop: This document outlines the prerequisites for using Autoscale. It explicitly states

"To use CPU utilization as a threshold

you must configure performance counters to collect and send data from your session hosts to the Log Analytics workspace associated with your scaling plan." This configuration is managed through the VM's diagnostic settings.

Source: Microsoft Learn

"Autoscale scaling plans and example scenarios in Azure Virtual Desktop

" Section: "Prerequisites."

2. Microsoft Documentation - Collect guest metrics for an Azure virtual machine: This guide details how to send guest OS performance counters to the Azure Monitor metric store or a Log Analytics workspace using Diagnostic settings and the Azure Monitor agent. This is the underlying mechanism required for the AVD Autoscale feature.

Source: Microsoft Learn

"Tutorial: Collect guest logs and metrics from an Azure virtual machine

" Section: "Enable diagnostic setting."

3. Microsoft Documentation - Overview of Azure Monitor agents: This document explains that agents are required to collect monitoring data from the guest operating system of virtual machines. Configuring Diagnostic settings on a VM installs and configures such an agent to collect performance counters.

Source: Microsoft Learn

"Overview of Azure Monitor agents

" Section: "Collect data from virtual machines."