Only 19 of the VMs on my VMSS are running. I want to run 80 instances for a university course

Hi ,

Thanks for reaching out to Microsoft Q&A.

The issue you are facing, where only 19 out of the 80 intended Virtual Machine instances in your VMSS are running while the rest show a “Failed” status, is most likely due to regional capacity constraints in the East Asia datacenter rather than a quota problem. Even though you have an approved quota for 80 instances of the Standard_B2s size, Azure still needs available physical capacity in the chosen region to fulfill the allocation request. When demand is high, smaller VM sizes like B-series can be particularly constrained in certain regions. To resolve this, you should either redeploy the VMSS to a different region with better availability (such as Southeast Asia or Japan East) or switch to a VM size with more available capacity in East Asia. Additionally, verify that your VMSS upgrade policy, OS image reference, and any startup extensions are not causing provisioning failures. You can confirm the exact reason by checking the Activity Log or using the Azure CLI to view the instance provisioning state, which will indicate if the error is due to allocation failure. If capacity shortage is confirmed, moving to another region or changing the VM size is the fastest way to run all 80 instances successfully for your course.

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Hi CS5285 CS5285,

The reason only 19 out of 80 VMSS instances are provisioned is most likely due to regional capacity constraints in the East Asia datacenter, rather than a quota problem.

Even if your subscription quota is approved for 80 Standard_B2s vCPUs, Azure still requires sufficient physical capacity in the chosen region or zone. When demand is high, certain VM sizes (especially popular ones like the B-series) may not be available in large quantities. In such cases, deployments beyond a certain threshold fail with errors such as Allocation Failed or Insufficient capacity.

For more information, refer here: Troubleshooting Azure VM allocation failures - Virtual Machines | Microsoft Learn

Follow the steps below to troubleshoot the issue:

1. Check provisioning errors:

• In the Azure Portal, go to your Virtual Machine Scale Set (VMSS)→ Activity Log.
• Check the Activity Log for failed instances.
• Errors like AllocationFailed or Insufficient capacity confirm the problem is a lack of available hardware(capacity) in the region.

1. Verify quota limits

• In the Azure Portal, go to Subscriptions > Usage + quotas.
• Filter by Location = East Asia.
• Verify both the B-series vCPU quota and the Total regional vCPU quota.
• If your quota is less than the required 160 vCPUs (80 instances × 2 vCPUs), submit a request to increase it.

For more information, refer here: Increase regional vCPU quotas - Azure Quotas | Microsoft Learn

1. Try scaling in smaller increments: Instead of a single scale-out to 80, try provisioning in smaller batches (e.g., 25-30 at a time) to take advantage of newly freed-up capacity.
2. Change region: Try Southeast Asia or Japan East, which may have better availability.
3. Change VM size: Use B2ms or a small D-series SKU if East Asia must be used.
4. Use capacity reservation: For predictable and long-term deployments, reserve the necessary capacity upfront to guarantee resource availability. For more information refer here: On-demand capacity reservation in Azure - Azure Virtual Machines | Microsoft Learn

 By confirming the error details, reviewing your quota limits, and adjusting either the region or VM size, you should be able to scale your VMSS to the desired 80 instances.If you still continue to see this AllocationFailed errors ,the best approach is to open a support request with Microsoft so the backend regional capacity can be reviewed and guidance can be provided on this issue.

Let me know if you require any additional information from my end. I happy to help you with the queries. If the information is helpful, please click on Upvote and Accept Answer on it so that it can help other community members.

Thank you,

Rashmika