Host Pool Azure Capacity Extender Configuration

Nerdio Manager allows administrators to specify additional VM sizes in the event that sufficient resources are not available in the Azure region to complete various tasks with the preferred VM size. This enables you to overcome Azure compute capacity limits by specifying multiple fallback VM sizes for use if the capacity is exhausted for your preferred VM size in the region. This ensures that hosts creation, auto-scale, auto-grow, and auto-heal operations do not fail due to Azure capacity constraints.

To configure host pool Azure capacity extender settings:

1. Locate the host pool you wish to work with.

2. From the more options menu, select Settings > Azure Capacity Extender.

3. Enter the following information:.

   • Azure Capacity Extender: Enable this option to enable this feature.

   • Host Pool Default VM Size: This VM size to be used, whenever possible, during Start and Create VM operations.

     Note: This is for reference only and cannot be changed here.

   • Alternate Preference VM Sizes: From the drop-down list, select the fallback VM size(s) to be used, in sequence, if the default preferred VM size is not available.

     Note:

     • Please ensure that you select VM sizes that match the resources of your preferred VM size. Using VM sizes with different resource profiles may impact user performance.

     • The icon indicates that the size and/or cost differs significantly from the default host pool VM size.

     • The list may be filtered using the Resource Rules selectors at the top of the list. See Resource Selection Rules Management for details.

     • You may drag & drop the alternate VM sizes to changes the order.

   • Allow resizing of hibernated VMs: Select this option to allow end users to use Azure Capacity Extender to resize hibernated VMs in the self-service portal.

   • Availability Zone Awareness: Select this option to provide increased redundancy and availability by allowing Nerdio Manager to consider all possible availability zones when reinstantiating VMs.

   • Note: For this setting to take effect, ensure that Distribute VMs across Availability Zones is turned on in Host pool VM deployment configuration.

   • Use Intelligent Azure Capacity Extender: Select this option to enable the Intelligent Azure Capacity Extender feature.

     Note: Nerdio Manager dynamically selects the appropriate resources in the event of a capacity issue with your default machine size. The VM size selection is dynamically based on the current running configured size of the virtual machines in the pool.

     • Manageable Restrictions: Enable this option to enable this feature.

       Note: Manageable restrictions allows you to fine tune configuration settings by specifying the CPU and GPU architectures that are allowed, as well as the maximum difference between the RAM and CPU cores.

       • Processor Type: From the drop-down list, select the processor difference allowed between the default VM size and the suggested sizes.

       • Number of Cores: From the drop-down list, select the maximum cores difference allowed between the default VM size and the suggested sizes.

       • RAM: From the drop-down list, select the maximum RAM difference allowed between the default VM size and the suggested sizes.

4. Once you have entered all the desired information, select Save or Save & close.

Azure Capacity Extender Logic

The following logic used by the Azure Capacity Extender when a session host VM does not boot because of a Microsoft capacity issues with Availability Zone Awareness enabled and disabled.

Initial conditions:

• Host pool default VM size: BS1

• Alternate Preference VM Sizes: BS2

• Enabled all zones in "Deploy VMs across availability zones" in Virtual Machines tab

• Zone 1 is the least used

• Zone 2 is moderately used

• Zone 3 is the most used

Scenario 1 - Availability Zone Awareness is enabled (new logic):

• Zone 1 is tried with Size BS1 → no capacity.

• Zone 2 is tried with Size BS1 → no capacity.

• Zone 3 is tried with Size BS1 → no capacity.

• Zone 1 is tried with Size BS2 → no capacity.

• Zone 2 is tried with Size BS2 → VM is created successfully → The task "Add host" is completed with a status of "Complete."

Scenario 2 - Availability Zone Awareness is disabled (old logic – pre -v7.4):

• Zone 1 is tried with Size BS1 → no capacity.

• Zone 1 is tried with Size BS2 → no capacity → The task "Add host" is completed with a status of "Error."

• (Zone 1 is the least used, so it was the only Zone that was tried)