Avamar: VSS Plugin Backup with HF 310901 Applied is not Completing with the Error "avvss Error 8784"

Environment:
Avamar 18.2 Windows VSS plug-in
Client running on Microsoft Windows 2016 operating system

Issue Scenario:

• The original issue was seen as:

ERROR: Win32 call L"GetVolumePathNameW"

• This issue was addressed by applying HF310901 as described in the KB article
  • Avamar: Windows VSS backup failing with - ERROR: Win32 call L"GetVolumePathNameW" failed
• However, after applying the HF as directed by KB article above, the below issue is seen:

avvss Error <8784>: BackupComplete(): Writer 'BITS Writer' instance '{..}' not found on system!

• This issue was addressed by applying HF312557 as described in KB article
  • Avamar: VSS plug-in backup failed with "avvss Error <8784>: ... Writer 'BITS Writer' instance 'xxxxxxxxxxxx' not found on system!." However, the backup appears in Restore GUI
• Applying HF312557 to resolve ERROR: Win32 call L"GetVolumePathNameW," the original BITS writer issue reemerges.

Engineering provided a solution that resolves both of the issues together.

The Microsoft Windows BITS Writer went offline completely or restarted during the backup, which caused the writer missing or writer's GUID change issue.

There are valid reasons for the BITS writer to go offline, for example when Windows Updates have a pending reboot.

For more info about BITS writer issue, see KB article.

• Avamar: VSS plug-in backup failed with "avvss Error <8784>: ... Writer 'BITS Writer' instance 'xxxxxxxxxxxx' not found on system!". However, the backup appears in Restore GUI

To resolve the Avamar Windows VSS BITS Writer is not found on the system and ERROR: Win32 call L"GetVolumePathNameW" failed

• Upgrade the Avamar Server to.
  • 19.4.100-124 or later
• The fix is in Avamar 19.4 and later software releases.