VM backups are getting failed as "An attempt to take a snapshot of a virtual machine failed because it was unable to quiesce an application". However, the backup is getting completed in next attempt or by rerunning it manually without troubelshooting anything. So, to mitigate this, we initially suspected the issue might be due to the VM tools or VSS writers of Guest OS and we have reinstalled VM tools with VSS writers option, but same issue araised again.
We verified the logs in the V-Center during the window of backup failure and found below errors in the V-Center and also noticed the VSS writers error in the event logs on the servers during the window of backup failures but, VSS writers are showing stable from guest OS.
Errors from V-center:
Description Type Date Time Task Target User
"Warning message from Vcentername: The guest OS has reported an error during quiescing. The error code was: 5 The error message was: 'VssSyncStart' operation failed: The service cannot be started, either because it is disabled or because it has no enabled devices associated with it. (0x80070422) " Warning 09/07/2019 17:24:39 Clienthostname vpxuser
An error occurred while quiescing the virtual machine. See the virtual machine's event log for details.
An error occurred while taking a snapshot: Failed to quiesce the virtual machine.
An error occurred while saving the snapshot: Failed to quiesce the virtual machine.
Backup Exec Version: 20.3
There are arount 50 VMs which are configured in 6 backup jobs and each backup job contains 6 to 10 VMs
Could you please help let us know what could be the reason for intermittent VM backup failures. What are logs we need to verify from Vcenter as well as from the guest OS.