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VSS errors related to SQL writer failure


You receive the following error during the guest processing:

Unable to release guest. Error: Unfreeze error (over VIX): [Backup job failed. Cannot create a shadow copy of the volumes containing writer's data. A VSS critical writer has failed. Writer name: [SqlServerWriter]. Class ID: [{a65faa63-5ea8-4ebc-9dbd-a0c4db26912a}]. Instance ID: [{6323fe10-0205-47df-b015-4a5ff60c31e2}]. Writer's state: [VSS_WS_FAILED_AT_PREPARE_SNAPSHOT]. Error code: [0x800423f4].]


This error means that the VSS writer responsible for the SQL server doesn’t work correctly. The error itself  is rather generic and can be caused by different reasons. One of them is an update of the Microsoft Azure AD Connect client.

If you recently installed this update, the repair of the SQL installation should fix the issue. If you didn’t, still try the below since it might also resolve other issues.

  • Go to Add/Remove Programs
  • Select Microsoft SQL Server 2012 Express LocalDB (or your actual SQL version)
  • Select Repair
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Note that it’ll require a reboot afterwards.
If it doesn't help, further SqlServerWriter troubleshooting will be required. Until the issue with SqlServerWriter is resolved, you can create crash-consistent backups by disabling the application-aware processing.

Veeam Backup & Replication
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