Symptoms
Hyper-V backups intermittently fail with errors similar to the following:
avhypervvss Error <42447>: Failed to complete operation on all remote client(s).
avhypervvss Error <41629>: Failed to gather status from remote clients
avhypervvss Error <41659>: Backup did not complete successfully
Cause
Subworkorder communication delays between primary and secondary nodes in the Hyper-V cluster.
Resolution
Edit the avhypervvss.cmd file in the shared var directory and add the following flag:
--subworkorder-timeout=20
This flag will allow the secondary node an additional 20 minutes to receive and acknowledge the subworkorder to the primary node. Increase the value if necessary.