Microsoft Hyper-V • Veeam Restore Hyper-V Failover Cluster High CPU

Hello,
is there a known issue around restoration of a Windows virtual machine into Hyper-V Failover Cluster (in our case, Azure Stack HCI 22h2) which might cause a whole cluster to go to high CPU usage?
Note that we did not remove the virtual machine from the failover cluster prior to restoring it. But also were not aware that this might be a needed thing to do. We have never done it before, for machine restores.
We have following suspicion:
When Veeam starts to restore a VM that is actively part of the FC, some (or all nodes) peak the CPU usage to 100%. If we are lucky, there are nodes that remain at low CPU usage, and we might be able to live migrate the VMs from the nodes that are 100%, thus lowering the CPU load.
The solution apparently is solved when any of the nodes is not at 100%, then the whole cluster calms down. One of the services that seems to be at top is clussvc.
This has now happened twice in connection with one VM restore, that was still part of the cluster.
Note that also, after restore, and even removing the VM that was restored, including removing from FC, and shutting it down and removing it from Hyper-V doesn't relax the situation.

We currently cannot ascertain for 100% that it is caused by this restore, because we also had issues without Veeam restoring, but the timing has been on spot the two times Veeam was involved.

Thanks

Statistics: Posted by kosta88 — May 05, 2025 11:14 am

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