Failed to start virtual machine

Question

While this machine was working for long time with, and turn off/on every day, we started getting this error when trying to start it:

Failed to start virtual machine '...'. Error: Allocation failed. We do not have sufficient capacity for the requested VM size in this zone.

Currently we are not able to start it anymore, the regional cpu limits are 4 which are enough to run this machine.

Answer 1

This error indicates a platform capacity constraint—Azure currently does not have available GPU (T4) capacity for this VM size in the selected region/availability zone. Quota increase only allows usage but does not reserve physical GPU hardware.

This commonly occurs with NC‑series GPU VMs, especially when a VM is started from a deallocated state, as Azure must re‑allocate actual GPU resources at that time.

Recommended actions:

• Try starting the VM in a different availability zone
• Resize to an alternative compatible GPU SKU
• Deploy/start the VM in a different region
• For production workloads, consider On‑demand Capacity Reservations to guarantee GPU availability
• This is expected Azure platform behavior and not a configuration or subscription issue.

Microsoft documentation:

• Troubleshoot Azure VM allocation failures: https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/windows/allocation-failure
• Improve likelihood of allocation success: https://aka.ms/allocation-guidance
• Capacity reservations overview: https://learn.microsoft.com/en-us/azure/virtual-machines/capacity-reservation-overview

Answer 2

Hi Iyad,

Due to limited available capacity, if you need to start the machine you will need to change it to a different size and then try to start it again. To do this you navigate to the VM in the Azure portal, on left click on Availability + scale -- Size, select a different VM size, and click Resize button at the bottom.

Once you get notification at top right that it has succeeded you may try to start the vm.

An alternative to the above would be to periodically try to start the VM in the hopes that capacity will be available. For example, if you try starting it during off hours for the region you will likely have better luck since usage is lower.

Please click Accept Answer and upvote if the above was helpful.

Thanks.

-TP