Symptoms
Hyper-V backups fail with the following errors:2016/02/26-05:32:20.10400 [hypervvss_assist] ERROR: COM call m_pVssObject->AddToSnapshotSet((LPWSTR)*(volume.to_uwstring()),vss_provider_guids[j], &SnapshotID) failed.2016/02/26-05:32:20.10400 [hypervvss_assist] - Returned HRESULT = 0x8004230d2016/02/26-05:32:20.10400 [hypervvss_assist] - Error text:VSS_E_OBJECT_ALREADY_EXISTS2016-02-25 21:32:20 avhypervvss Error : Unable to expand backup targets...2016-02-25 21:32:20 avhypervvss Error : Could not expand targetscorrectly....2016-02-25 21:32:20 avhypervvss Error : Backup did not completesuccessfully.
Cause
1. Multiple mount points pointing to the same hard drive volume. VSS plug-in builds up a list of affected volumes that need to be in the snapshot. If two different paths pointing to the same volume are included in this list, the backup will result in a VSS error and a failed backup.2. Possible code bug in Avamar v7.0 of the Hyper-V VSS plug-in.
Resolution
Perform the below steps:
Remove the redundant mount point. Upgrade to a newer version of the Hyper-V VSS plug-in. The latest version available is 7.2.101-32.
