- You are backing up a virtual machine with Windows Server 2019 on ESXi 6.5 or 6.7 using Agent for VMware (Windows) or Virtual Appliance,
- Agentless backup finishes with warning
Creating a crash-consistent snapshot of virtual machine because the creation of its application-consistent snapshot has failed. An error occurred while saving the snapshot: Failed to quiesce the virtual machine
(!) Note that this issue is specific to Windows 2019. If this error occurs in a VM with a different OS, please see this article instead: Acronis Backup: backup finishes with warning "Creating a crash-consistent snapshot of virtual machine because the creation of its application-consistent snapshot has failed"
This issue occurs because Windows 2019 cannot support the recovery volume that is included into the VSS SnapshotSet during the VSS process.
See details in this VMware KB article.
1) If you have transactional applications on the VM and also want to create an application-consistent backup
Please install the agent for Windows and for the transactional application inside the VM and back up the machine by this agent. See Adding a machine running Windows for instructions.
In this case the machine snapshot is taken directly by Microsoft VSS in the operating system, bypassing the issue with quiescing.
2) If you do not have transactional applications like SQL, Exchange or Active Directory on the VM
When it comes to a general backup, you can simply disable the machine quiescing and back up the machine with the file system-aware snapshot.
To disable quiescing, select the backup plan in Management Console, click Edit in the menu on the right and then click the "gear" icon to modify backup options, and switch off Volume Shadow Copy Service (VSS) for virtual machines. Please see product documentation for more information.
As a result, the software will not attempt to create application-consistent snapshots and there will be no warnings caused by VMware limits associated with agentless backup in such a scenario.