Recurring Allocation Failures for NCasT4_v3 GPU VMs in Sweden Central – Capacity Stability, Reservations, and Cross-Region Migration Guidance

The recurring allocation failures you are experiencing with NCasT4_v3 GPU VMs in the Sweden Central region can be attributed to insufficient resources in the availability zones you are utilizing. This is a common issue when demand exceeds the available capacity for specific VM sizes in a given region or zone.

Recommendations for Mitigation:

1. Retry Allocation: Sometimes, simply retrying the allocation request can help, as resources may become available after a short period.
2. Resize the VM: Consider resizing your VMs to a different size that may have more availability in the region or zone. This can help alleviate the allocation issues.
3. Change the Region or Zone: If the current region or zone continues to experience high demand, you might want to deploy or migrate your VMs to a different region or availability zone where there is more capacity. This can be done by creating a new VM using a copy of the OS disk in the new zone or region.

Migration Guidance:

For migrating your environment across different regions while retaining managed OS and data disks, as well as network interfaces, you can follow these steps:

• Create a Snapshot: First, create snapshots of your managed disks.
• Create a VM from Snapshot: Use these snapshots to create new VMs in the target region.
• Networking Considerations: Unfortunately, when migrating VMs across regions, you cannot retain the same private or public IP addresses. You will need to reassign IP addresses in the new region, as there are no supported methods to migrate IP addresses while preserving them.

Conclusion:

Given the current capacity constraints in the Sweden Central region, it may be beneficial to explore other regions for more stable GPU availability. If IP reassignment is unavoidable, plan for this in your migration strategy to minimize disruption to your development teams.

References:

• Troubleshoot allocation failures when you create or resize VMs in Azure
• Fix an AllocationFailed or ZonalAllocationFailed error when you create, restart, or resize Virtual Machine Scale Sets in Azure

Hello @Esraa Sayed ,

Whether there is a supported approach to migrate VMs across regions while retaining IP addresses (private and/or public), or whether IP reassignment is unavoidable in cross-region migrations.

Unfortunately, it's not possible to keep the same IP addresses because of platform limitations with Azure Networking services.

Explanation:

-> Private IPs are linked to subnets within a VNet, and VNets are specific to regions. If you move or recreate a VM in a different region, it must use a new VNet, so the original private IP can't be kept.

-> Azure Public IPs are also region-specific. A public IP created in the Sweden Central region can't be transferred or used with a VM in another region, so it can't be retained during migration.

Then how to do migration without affecting users?

Rather than using the raw IP, consider placing the VM behind one of the following:

• Azure Load Balancer
• Azure Application Gateway
• Azure Front Door (global)

Direct users to a DNS name instead of the IP address.

During migration, simply update the backend, and users will not experience any changes.

Hope it helped to answer your query, let me know if there are any more questions around it.

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