The error “Snapshot_vss - vss failed to prepare snapshots for backup” typically occurs when the Volume Shadow Copy Service (VSS) within the operating system is unable to create a snapshot of the drive for backup.
VSS is a Windows Service that provides the ability to create a point in time image (shadow copy) of one or more volumes that can be used to perform backups. The service is also used during restores of applications.
When a backup job runs, it uses VSS to create a snapshot of the disk data at a specific point in time. This allows the backup process to capture a consistent “picture” of the data that is being backed up, without worrying about changes that may happen while the backup is running.
In some cases, VSS might fail to prepare snapshots for backup due to various reasons such as:
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Check the Event Log: Look into the event log inside the VM. This can often provide more information about the error.
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Use Windows Server Backup: Try using Windows Server Backup within the VM as a test.
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Update Hyper-V Integration Services: Ensure that you’ve updated the Hyper-V Integration Services to the latest version.
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Run Acronis VSS Doctor: This tool can diagnose and repair some common issues with VSS.
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Check for Scheduled Backups in SQL Management: If you have a scheduled backup running in SQL management, it might cause VSS to struggle by locking certain files.
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Clean Up VSS Writers: Try cleaning up the VSS writers.
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Modify Registry Settings: Navigate to “HKEY_LOCAL_MACHINESystemCurrentControlSetServicesVSSSettings” in regedit.exe and create a new DWORD value named “IdleTimeout”. Change its value to 1,200,000 in decimal (20 mins, default is 10 mins).
You can resolve this by doing as suggested in the above. However, ensure that you have also backed up your data before attempting to fix the error “Snapshot_vss - vss failed to prepare snapshots for backup” or change anything on your systems.
