What are the best practices to ensure Agentless backups run without any issues?
- Agentless backups
Common causes of issues on Agentless backups
Changing virtual Disk sizes
Check that the volume’s virtual disk size is set to a whole number. Any storage set to a fraction of a GB throws a fractional size error, which can result in the Invalid Root File System message.
If the volume is set to a fraction, round the space up to the next GB.In the image above, you'd change the storage to 36 GB.
Address any "Disk needs consolidation" messages as necessary
If you see a "Disk needs consolidation" message, consult this article.
Snapshots are useful as a secondary backup method for short-term or ad-hoc backups. Keeping snapshots for a long period of time will negatively impact the performance of your production VMs. Finally, consolidating a virtual disk that has long-term snapshots takes a very long time, and can cause a negative impact on the I/O performance of that VM.
By default, the snapshots taken by Datto appliances persist for only as long as it takes to back up any given target virtual machine.
Differential Merges should not be run on Agentless.
If you do enable a differential merge for the next backup and it experiences issues, please reach out to our support team.
Verifying quiescing is enabled
The Datto solution leverages a VMware feature called quiesced snapshots. When taking a quiesced snapshot, VMware pauses writes to the virtual machine's virtual disk to achieve a consistent state. To back up a Windows guest OS, the Datto solution also uses the virtual production machine's VSS writers. If a quiesced snapshot of a VM fails to complete, a backup job will not run. Without quiescing, VMware snapshots are only crash-consistent.
Changing VM Templates
CBT (Changed block tracking) needs to be enabled for incremental agentless backups to function, that requires a VM template of at least version 7.