windows_exporter/docs/runbooks/windowshypervreplicationcritical.md

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WindowsHyperVReplicationCritical

Meaning

Hyper-V Replica reports critical health for the virtual machine vm for five minutes. The alert carries the relationship label, primary for the normal replication and extended for an extended replica, and needs the hyperv collector with its replica_vm subcollector. Critical health means that replication has not succeeded for long enough that the replica misses the recovery point objective, or that replication is paused because of an error.

Impact

The replica of the virtual machine is stale. A failover to it loses the changes since the last successful replication, and the recovery point objective of the service is not met. If the primary host fails now, data is lost.

Diagnosis

1. Inspect windows_hyperv_replica_vm_health and windows_hyperv_replica_vm_state for the virtual machine; the state tells whether replication is suspended, resynchronizing or in error, and windows_hyperv_replica_vm_replication_latency_seconds how long the last cycle took.

2. On the primary host, read the replication details:

   Measure-VMReplication -VMName '<vm>' | Format-List *
   Get-VMReplication -VMName '<vm>' | Format-List State, Health, LastReplicationTime, ReplicationMode
   Get-WinEvent -LogName Microsoft-Windows-Hyper-V-VMMS-Admin -MaxEvents 50 | Where-Object Message -like '*<vm>*'
   

3. Check the replica server: free space on the replica storage, the Hyper-V Replica HTTP or HTTPS listener, the certificate for authentication, and the network path between the hosts. Check whether a snapshot merge or a storage migration on the primary blocks replication.

Mitigation

Fix the cause on the replica server or the network, then resume replication with Resume-VMReplication -VMName '<vm>'; add -Resynchronize when the state asks for a resynchronization. Confirm the health returns to normal and the last replication time advances. If the replica cannot be recovered, remove and re-enable replication, which sends a full initial copy.