Hyper-V stuck on 'Applying Replica CHanges'

Hi,

Thank you for your posting!

Based on your descriptions, your issue is related to the failure to apply changes of your replicated VMs. There are many factors that could cause your issue, including No Adequate Network Bandwidth between Primary and Replica Server, Not enough storage on Primary Server or Replica Server to store HRL files, etc. And the article below may help you conduct relevant troubleshooting:

https://www.altaro.com/hyper-v/advanced-troubleshooting-of-hyper-v-replica-part-3/

(Please note: Information posted in the given link is hosted by a third party. Microsoft does not guarantee the accuracy and effectiveness of information.)

If you still cannot solve your issue, you may try this blog as well:

https://social.technet.microsoft.com/Forums/en-US/fd0d462d-9c68-4ab9-808e-b61e6a3d65a1/hyperv-failed-to-replicate-changes-for-virtual-machine-server-because-too-many-logs-are-pending-on?forum=winserverhyperv

Beside, you can try to find some relevant error codes or message in your Event Viewer to better determine the scope of your issue. Go to Event Viewer>> Applications and Services>> Microsoft >> Windows>> Hyper-V VMMS. You can always give me the error codes and messages and I will try my best to help you.

Thank you for your support!

Best regards
Joann

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Hi,

Thank you for your reply!

Based on your descriptions, you can firstly try to kill the replication process in your Task Manager>> Process. You can press Ctrl+Shift+Esc to open your Task Manager. Then just right click the process and choose "End Task". Close your Task Manager and the replication process should be closed.

If you still cannot end your replication process, you may have to reboot your server.

Thank you for your patience!

Best regards
Joann

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Hi,

Thank you for your reply!

Based on your descriptions, if directly killing the process in Task Manager doesn't work, then it seems that your kernel hung when your replica process tried to apply changes to the replicated vhd files. You can try to log out your account to see if it works. Otherwise, after research, rebooting the server seems to be the appropriate way.

In addition, based on your condition, "Then if I reboot the server, all the replicas go mad trying to sync and a different VM will get stuck on the same problem and so on," I suppose rebooting is not enough and you may need further investigation on your issue. For instance, your issue may arise from unstable hardware devices, out-of-date device drivers, third-party program interference, system abnormalities, etc.

Then you may need to seek inquiry from your hardware retailer or third-party retailer, or you can try to seek direct assistance from our Microsoft Support Engineer through Microsoft Customer Support Services. You can contact Microsoft Product Support directly to discuss additional support options you may have available, by contacting us from the options in the website:

https://support.microsoft.com/en-us/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2

Thank you for your understanding and support!

Best regards
Joann

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Hello @JiayaoZhu

Thank you for your reply.

Rebooting a production server does not seem like the correct solution and I do not believe this issue is isolated to my servers (various servers, not just one). FOr information, all drivers, OS and patches are up to date.

I see this has been an ongoing issue that has not been resolved as others have reported the same problem without resolution : https://social.technet.microsoft.com/Forums/en-US/f78e478b-8c9d-4e7f-a968-03b3c5f27a2a/replicated-guest-stuck-merging-on-hyperv-core-2016?forum=winserverhyperv

Thanks for your time.

@JiayaoZhu
I'm just now experiencing this same issue on a 2016 host, where each of 3 reboots has left one of my VM replicas in Warning state "Applying Replica Changes". This is not a resource issue on my host. I'm not sure if the recent november update has any relation in my case since thats all that changed recently. I have tried killing and restarting the vmms process/service and that just seems to cause more problems with merges, so in my case reboot seems to be the only solution at this point which I also agree is unacceptable for a production server. I believe something is happening with the hyper-v service during the normal replication and "applying replica changes" that isnt being recorded as an error anywhere and its just stuck in that state until the next reboot, and I also have seen this occur on a different VM after reboot. I finally got to a clean state after pausing replication on one that was stuck this way, rebooting, and resuming replication.