About the '_exclude' LUN.
During Autorecovery VSS asks VSS hardware provider to mount the first snapshot(backing).
Snapshot mount is done with a LUN clone created in the active file system. During the mount the original LUN is renamed as lun-name_exclude and the LUN clone is renamed as LUN.
The VSS writer then does auto-recovery to revert the hardware snapshot to the software snapshot taken earlier.
When auo-recovery is complete we take the second snapshot (_backup suffix). After the second snap is complete, LUN is renamed back to the original name.
So in short _exclude is the original LUN in first snapshot. The autorecovery phase renames the original lun to "Lun-name_exclude" so that it will be excluded
for the ndmp dump utility. The clone created for autorecovery will have the name of the original lun.
Following link has more details about the changes required to support the NDMP dump.
http://wikid.netapp.com/w/SnapDrive_for_Windows/VSS/VSS_Autorecovery_ERRD#Standard_NDMP_Dump
Thanks,
Vineeth