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We're having a problem with a Windows Server 2025 Hyper-V cluster.
We have 2 identical clusters (same hardware, same BIOS version) and when we move a Windows 2012R2 VM from one cluster to another it does not boot any more (tested with 2 different VM's).
The error is a blue screen 0x7B (INACCESSIBLE_BOOT_DEVICE).
If we move the machine back to the other cluster it boots just fine.
Only difference I see is the cluster path level. The working cluster is an older Windows Update (KB5058411, KB5058523 and KB5054979).
Whereas the newer cluster has KB5063666, KB5062553, KB5056579 and KB5059502. It tried installing KB5064489 also, but that does not help.
A VM with Windows server 2022 of 2025 does move fine, so it seems to be linked to 2012R2.
I also tried to install a brand new 2012R2 VM from the original iso and then completely upgrading it with Windows Update and that machine is working fine. It seems to have the same verson of storage drivers as the non working VM.
The faulting VM does boot succesfully into recovery mode. I tried bootrec /fixmbr and bootrec /fixboot, but that does not help.
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Same issue here. Sadly I could not pin down the exact faulty update!
but thanks for your direction!
Thought, I killed my VM. Even the back up…. :D
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Hi Guys,
So after a 7 hours call with MS still no solution. We checked so many things but not booting. My thanks go out to the engineer who helped me!, he will need to get into contact with his technical manager and see where to go from here.
Seems like a very annoying issue.
Hope to get some updates here soon, in the meanwhile thank you everyone for the posts here!
Regards
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Seven hours, wow! Thanks for your perseverance Peter.
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Hi Peter, no more updates MS side?
Hi Dimitri,
Unfortunately not, because we troubleshoot it a long time the MS engineer had to consult with his technical manager. First response was, no extended support, no support so it's looks I'm stuck on the MS side (for now).
I'm getting as far with this that for some reason some registry key looks not accessible when the VM is moved. I ran some diagnostics tool I got from MS and this is the only difference we notice. I totally don't understand why a registrykey inside the VM changes/is not accessible when moved. Maybe it has to do with driver signing/certificates that are expired I don't know. The tool boots a PXE environment so I'm not sure how this can be related. What makes it more difficult is that a clean install of 2012R2 works and in our case 'some' of the moved 2012R2 servers don't boot, not all, so very unclear.
Regards,
Peter
Thank you for the update.
In my case 100% of the moved vms are not booting, but are only 3 fortunately. Freshly installed vms boots correctly.
The problem is occurring also exporting the working vm and importing to a 2025 host.
The registry error is very strange, a more detailed error than "cannot find the file specified" would have been more helpful :)
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hello,
I also managed to get on the phone with MS support, but they quickly mentioned 202R2 lifecycle and that was that.
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Question, do we have the same issue on windows 2022, don't want to go all the way back to 2019 if not needed.
Also, I can add that one suddenly did work, then didn't work again after a reboot having me wonder if it was something else in the hyper-v setup, boot order of VMs. Sorry nothing confirmed yet from that as that one still doesn't work but thought to mention.
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Hi Richard,
We moved around 300-400 non 2012R2 VM's from 2022 host clusters to 2025 host clusters now and there doesn't seem to be an issue with these (knock knock on wood). So 2012R2 VM's where running fine on 2022 hosts with all the latest patches as far as I can tell.
given they (2012r2 vms) run fine on 2022 (assuming fully patched), have you tried moving one of them to a 2025 host to see if that works? Good to know 2022 works.. I may try firing up a 2022 host server instead of 2019 to move forward at least.
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I too have the same issue, tried copies, Veeam replication, Veeam backups, still not found a solution.
Some of the issues I'm seeing in Veeam point to version issues, here is the link to the Veeam KB, but so far I'm still having issues.
2012r2 vm on 2022 host has no issues, we ran the 2012r2 vms for a long time. Migrate to 2025, boot issue. Veeam also tried without Success. For testing i tried to run the 2012r2 vm on my windows 11 workstation, also does not boot, easy to continue testing on my local workstation
I'm wondering if I can do a cold backup on Veeam, restore to VMware, backup again with Veeam and the restore to 2025 Hyper-V Host
In Veeam I can perform a cold backup. Within Veeam I can then export the files from the C:\ drive to a new VHD, VHDX of VMDK. I have then used these to try and boot a brand new VM on my 2025 hosts, with Gen 1 and Gen 2 VMs. No Joy, still the same issue with the VM going into recovery mode. Unfortunately I'm not able to test the VMDK due to being off site but hope to this soon. This really feels like it has to be an issue inside of the source VMs OS, that the 2025 hosts see as some sort of corruption and will not boot.
If you look back to some of the previous comments, you'll will see that we have established it is KB5060842 introduced in June 2025 where the problem first occurred. Of course July 2025 KB5062553 also has the problem. Prior to this, all was good. I'm struggling to see how the MS Engineer couldn't understand this.
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I think they do Andy but because 2012R2 EOL finished in 23 they don't want to make their updates backwards compatible, my thoughts on it.
So after a staggering 5 hour call today, the support engineer is out of options. He really need to contact the 2012R2 support team but can't because we have no extended support. My thanks goes out to the Microsoft engineer for his help. Unfortunately we keep stuck at the VMBus message. For now we go with the option to run a server 2022 host nested on the 2025 host, same as Hammer.
Their response is terrible. They introduced the problem with a Windows update, they should fix it. Especially as 2012R2 is listed as a supported VM guest.
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If it’s a matter of drivers, is it possible to update them while the vm is running and then move to Server 2025 host?
Hi, having the same issue…any update on a possible solution? For now, I’m running the Server 2012R2 VM nested inside a Server 2022 VM under a Server 2025 host just to be able to have it up. There’s a huge performance penalty so would be great to find a better solution.
