Answering my own question,
This was resolved by turning off multistreaming for this policy. With
multistreaming, a separate stream was spawned for each drive, even if
the drive was filtered out and gave errors with the synthetic.
This problem did not occur when the policy was set to not use
multis
Okay,
so I have a problem with backing up MSCS clusters with ALL_LOCAL_DRIVES
backup selections.
The cluster nodes not holding the volume attempt to backup the volumes
and fail. This was easy enough to fix with policy specific client
exclusions, and these exclusions for the clustered volumes get
