Agent-based backup fails with "Usnap is not able to create a volume shadow copy"
Windows agent-based backups fail with "Usnap is not able to create a volume shadow copy" error.
Please use this KB when addressing this issue, please note that this process gives the server more time to complete VSS operations and may not resolve the underlying problem. When encountering VSS errors in backups it is always helpful to look for errors in VSS operations in Windows Event Viewer.
To resolve USNAP volume shadow copy failure on Windows clients, on the client server having the backup errors:
- Open C:/PCBP/MASTER.ini in a text editor, as an administrator.
- Find the [usnap] section and increase the following values by 600 (be sure to add 600 to the existing value):
USnapEnable=TRUE USnapKeepalive=1800 ; increased value by 600 USnapMutexTimeout=1420 ; increased value by 600 USnapVssAsyncFinished=1200 ; increased value by 600 USnapProvider=System ; add if there are multiple VSS Providers
- Save the MASTER.ini file.
- Restart the "bpagent" service. This will ensure the changes are registered and applied.
USNAP timeout condition occurs before snapshot completes.
For more detailed information on backup failures and performance issues see Unitrends KB 5062 - Backup Failures and Performance Issues