Introduction
Azure Virtual Desktop (AVD) is a powerful platform for virtual desktops and applications. One of the most important features in AVD environments is autoscaling of available session hosts. This helps optimize costs by automatically shutting down unused hosts and restarting them when needed.
But what happens if there are not enough resources available in a region or zone? This exact issue occurred in several Azure regions during 2024 and 2025. In this article, we will look at the existing autoscaling options, the challenges caused by capacity shortages, and how Nerdio solves these problems with the new Availability Zone Awareness logic introduced in version 7.4.
Why Autoscaling in AVD Is Important
Session hosts incur costs even when they are not in use. Autoscaling ensures that:
- Unused VMs are shut down.
- New hosts are automatically started when demand increases.
This saves costs and increases flexibility. Without autoscaling, administrators would have to perform these tasks manually – a significant effort.
Options for Autoscaling
Custom Solution
Organizations can develop their own scripts or automation, for example, using:
- Azure Automation Runbooks
- Logic Apps
Disadvantages:
- High complexity
- Maintenance overhead
- Required expertise
This approach is rarely the best choice in practice.
Microsoft Scaling Plans
Microsoft offers two types of scaling plans:
- Power Management: Turns hosts on or off based on schedules.
- Dynamic Scaling: Responds to user load and dynamically adjusts the number of hosts.
These solutions are easy to implement but less flexible. They do not account for complex scenarios such as capacity shortages in specific regions or zones.
Nerdio Auto-Scale
Nerdio significantly expands the possibilities:
- Dynamic start and stop of VMs based on parameters such as user load and performance.
- Distribution of session hosts across multiple Availability Zones within a region.
- Integration with Azure features for maximum resilience.
- Adding additional hosts when capacity runs low (burst).
This makes Nerdio a much more robust solution compared to Microsoft’s standard options.
The Problem: Capacity Shortages in Azure
Azure regions and zones do not have unlimited resources. During peak times, a VM may fail to start because the desired size is not available in the zone.
Example:
- Zone 1 has no capacity for the standard VM size.
- Zone 2 and Zone 3 are also overloaded.
Without intelligent logic, the attempt to start a VM ends in an error, and users wait in vain for additional hosts.
Azure Capacity Extender
With the Azure Capacity Extender, Nerdio takes autoscaling a step further to address Azure capacity shortages. If a SKU is not available in a region, the system falls back to configured alternative SKUs. This ensures that processes such as host creation, autoscaling, auto-expansion, and auto-healing are not disrupted or interrupted by Azure capacity limits.
This allows organizations to keep their AVD environments stable even during periods of high demand.
Before Version 7.4 (Old Logic)
The autoscale logic only checked the preferred zone:
- Zone 1 is tried with size SKU 1 → no capacity.
- Zone 1 is tried with size SKU 2 → no capacity.
Result: Error, VM is not created or started.
Azure Capacity Extender with Availability Zone Awareness
This new option allows Nerdio Manager for Enterprise to increase redundancy and availability by considering all possible availability zones when instantiating new VMs.
From Version 7.4 Onward (New Logic with Availability Zone Awareness)
The new logic checks all zones and alternative VM sizes:
- Zone 1 with SKU 1 → no capacity.
- Zone 2 with SKU 1 → no capacity.
- Zone 3 with SKU 1 → no capacity.
- Zone 1 with SKU 2 → no capacity.
- Zone 2 with SKU 2 → VM is successfully created.
Result: The task “Add host” or “Start VM” completes successfully, and the environment remains available.
This intelligent distribution greatly increases the chances that new hosts can be started even during capacity shortages.
Conclusion
Autoscaling is essential for an efficient AVD environment. While Microsoft Scaling Plans provide a basic solution, Nerdio goes much further:
- Greater flexibility
- Zone awareness
- Handling of capacity shortages
With the new Availability Zone Awareness logic introduced in version 7.4 and the Azure Capacity Extender, Nerdio is the best choice for organizations that want to combine high availability with cost efficiency.