SIRIS, ALTO, and NAS: Error: "Exception caught during backup run: File system not recognized for [GUID]"



When you try to start a backup for a system protected by the Datto Windows Agent, you receive the error message, "Critical error during data transfer." On investigation of the agent logs, you see the following error recorded: "Exception caught during backup run: File system not recognized for [GUID]."


  • Datto Windows Agent


One or more ReFS volumes on the protected system have unrecoverable filesystem issues present.

The Windows Event log may look something similar to the following:

Log Name: System
Source: ReFS
Date: 4/18/2019 11:58:30 PM
Event ID: 133
Task Category: None
Level: Error
Computer: <Redacted>
Description: The file system detected a checksum error and was not able to correct it. The name of the file or folder is "<unable to determine file name>."


Identity The Issue

Identify the volume having the issue (use the GUID to determine what volume it is) and exclude that volume from backups to confirm.

  • To find an event, you can review the agent log by navigating to your Protect Page → Show Backup Logs → Show Agent Logs
  • You can review the system logs to find an event, such as the one listed above. You can find Event logs in the partners' event logs at the same time as backups are trying to run. 

Resolve The Issue

To resolve the issue, you must wait for the Resilient File System to heal itself automatically. Eventually, the ReFS volume should resolve the file system issue by itself, and backups should be able to complete on the volume again. 

  • Once the filesystem heals, you will need to re-include the excluded volumes before they begin backing up again; they will not be re-included automatically.
  • To tell if the issue has been resolved, test to see if backups complete on the volume.

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