HYPERV live migration between 2 differents intel processor failed

Question

Hello,

I have a cluster with 4 hyper V.

I have 2 servers with a GenuineIntel Intel64 Family 6 Model 85 Stepping 4 processor,

and the 2 others with GenuineIntel Intel64 Family 6 Model 85 Stepping 7 processor.

Since i migrated my hyperV servers from 2016 to 2019, the live migration between the servers with differents processors failed. (error 21502).

The compatibility box is checked.

I would like some help.

Thanks.

Answer 1

The error code 21502 you are encountering during live migrations in Hyper-V usually relates to processor incompatibility between the source and destination hosts. In your case, the different processor stepping levels (Stepping 4 and Stepping 7) may be causing this issue.

Here are some steps you can take to address this problem:

Processor Compatibility Mode:

• As you mentioned, make sure that the "Processor compatibility" option is enabled for the virtual machines (VMs) that you're trying to live migrate. Enabling this option can help with migrating VMs between hosts with different processor versions.

Update Hosts and VM Configuration:

• Ensure that both the source and destination Hyper-V hosts are running the latest firmware, drivers, and Windows updates. Keeping both hosts up to date can improve compatibility.
• Verify that the VM configuration version is compatible with both Hyper-V hosts. VMs created in older versions of Hyper-V may not be compatible with newer hosts. You may need to upgrade the VM configuration version if necessary.

Use PowerShell for Migration:

• Try using PowerShell for live migrations. You can use the Move-VM cmdlet with the -IncludeStorage parameter to perform the live migration. PowerShell provides more control and flexibility over the migration process, and it may help overcome compatibility issues.

Processor Features and Compatibility:

• Check if there are specific processor features enabled or disabled in the VM settings that are causing the compatibility issue. Make sure that any processor-related settings are consistent between the source and destination hosts.

Processor Compatibility Mode Overrides:

• In some cases, you may need to specify processor compatibility mode overrides for individual VMs. This can be done through PowerShell using the Set-VMProcessor cmdlet with the -CompatibilityForMigrationEnabled parameter.

Check Hyper-V Logs:

• Examine the Hyper-V event logs and look for specific error messages or warnings that provide more information about the compatibility issue. This can help pinpoint the exact cause.

Processor Microcode Updates:

• Check if there are any microcode updates available for the processors on your hosts. Microcode updates can sometimes address compatibility issues.

Contact Vendor Support:

• If you continue to experience issues, especially due to processor-specific compatibility problems, consider contacting Microsoft Support or the hardware vendor for further assistance. They may be able to provide specific guidance or updates to address the issue.

It's worth noting that live migrations between hosts with different processor versions can be challenging, as compatibility issues can arise. Ensuring that both hosts are as similar as possible in terms of processor features and configurations can help mitigate these issues.

Answer 2

We are now in the process to replace the 4 server with newer ones. There is no solution coming from HPE or Microsoft. They closed the calls.

https://learn.microsoft.com/en-us/troubleshoot/windows-server/virtualization/troubleshoot-live-migration-issues

Answer 3

I have the same problem as everyone else, in my case this does not manifest until you have the following:

MS Failover Cluster running in Functional Level 11 (2022) // I'm testing in place rolling upgrade and found this issue.

All hardware nodes are identical server chassis mfg, model, bios level, CPU (speed, gen, model, stepping)

Windows Server 2022 Datacenter node

Windows Server 2025 Datacenter node

VMs of these types:

Gen1 version 10.0 and earlier, will live migrate from Server 2022 to Server 2025 while CPU Compatibility mode is ON or OFF.

Gen2 version 9.0 and earlier, will live migrate from Server 2022 to Server 2025 while CPU Compatibility mode is ON or OFF.

Gen2 version 10.0 will not live migrate while CPU Compatibility Mode is ON from Server 2022 to Server 2025.

Gen2 version 10.0 will live migrate while CPU Compatibility Mode is OFF from Server 2022 to Server 2025.

None of the combinations above will live migrate from Server 2025 to Server 2022 regardless of CPU Compat Mode (ON or OFF), Generation or Configuration Version

All combinations will live migrate between same Hyper-V Host OS (2022->2022 and 2025->2025) regardless of CPU Compat Mode (ON of OFF), Generation or Configuration Version

You don't even need an OS installed in the guest. You can just have it in the Generation, Config Version and CPU Compat mode sitting in a failed to boot up state and it behaves the same, so it's not some product of the guest OS.

Given that my underlying hardware for all four nodes in both clusters (two nodes per cluster) is identical and I'm running in to this, I'm not really buying the "it's a hardware issue" since it only manifests when a VM is built at or upgraded to version 10.0 and is also a Generation 2 VM.

Additionally, you can even live migrate, cross-cluster, a VM between these two clusters from Windows Server 2019 to Windows Server 2022 and back to Windows Server 2019 without issue.

This issue does not happen on Windows Server 2019 / 2022 in Functional Level 10 for me. All VMs even with CPU Compat ON live migrate from 2019->2022->2019 without issue on the same hardare as the cluster above as I have 4 identical servers.\

Again, same exact type of hardware, bios, patch level, etc as the two nodes above because they were all one cluster originally. In that mode, it was two Server 2022 and two Server 2025 and the same patterns of success/fail happened, so it's 100% an issue with Gen2, config 10 and moving from Server 2022 to Server 2025.