VSS Writers remain in "Waiting for completion" after successful backup or System Restore Point creation

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Thank you for providing the detailed test results.

Yes, this behavior can be expected and does not necessarily indicate a VSS problem.

State [5] = VSS_WS_WAITING_FOR_BACKUP_COMPLETE ("Waiting for completion") means that the writer is waiting for the VSS requester to signal that the backup operation has completed. This is a valid state in the VSS writer state machine and is not considered an error. When Last error = No error, the writer has not reported a failure.

In the VSS workflow, BackupComplete is a separate phase that occurs after the snapshot has been created. Writers return to Stable only after the requester completes the backup sequence and sends the appropriate completion notifications. BackupComplete can be described as a distinct step in the VSS backup process.

Based on your testing:

• Backup and System Restore Point creation complete successfully.
• No VSS errors such as Event ID 8193 or 12289 are logged.
• SQL Writer Freeze (3197) and Resume (3198) events occur normally.
• No orphaned shadow copies remain.
• The behavior is reproducible across multiple systems, including a system without Synology Drive installed.

These findings do not suggest a malfunction within the VSS framework.

The conditions that would be more concerning are:

• Writers remain in Waiting for completion and subsequent backup operations begin to fail.
• Writers report a Failed state or a non-zero error.
• VSS-related errors appear in Event Viewer.
• New backup jobs are unable to create snapshots until VSS services are restarted or the system is rebooted.

Therefore, a successful backup or restore point operation is generally a better indicator of VSS health than the writer state immediately after the operation completes. While many writers eventually return to State [1] Stable, please does not state that every writer must immediately return to Stable after every successful VSS operation. If backups continue to succeed and no VSS errors are reported, the behavior you observed is generally considered expected.

For additional information, please visit: VSS_WRITER_STATE (vss.h) - Win32 apps | Microsoft Learn

SQL Server Backup Applications - Volume Shadow Copy Service (VSS) and SQL Writer - SQL Server | Microsoft Learn

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