SIRIS, ALTO, and NAS: Error: Backup failed because the agent was unable to access a necessary file path on the protected system



When you try to start a backup for a system protected by the ShadowSnap agent, you receive the error message, "Backup failed because the agent was unable to access a necessary file path on the protected system."

In legacy versions of the Datto IRIS environment, this error message was, "Final Error: #2 The System Cannot Find The File Specified."


  • ShadowSnap Agent


  • There may be a damaged disk on the protected machine or bad sectors on the physical layer of a protected volume.
  • There could be a corrupt ShadowProtect installation or other conflicting ShadowProtect installs. 
  • There is Insufficient space in shadow storage to use the VSS snapshot during the ShadowProtect backup process. See this StorageCraft Knowledge Base article (external link) for more information.
  • Security or anti-virus software is blocking access to ShadowProtect on the server.


  1. Ensure that there is a public DNS entry in Datto appliance's Networking tab.
  2. Check the agent version running on the production machine, and update it if necessary.
  3. Make sure that no previous versions of ShadowProtect are installed and that no ShadowProtect backup jobs are running.
  4. Verify that directory C:\Program Files (x86)\StorageCraft is whitelisted in any anti-virus software.
  5. Check Device Manager for any abandoned 'StorageCraft Snapshot' devices. These may be listed under 'Other devices' or 'System devices' and may require enabling 'Show hidden devices.' If they are grayed out, right-click on the item and then choose Uninstall.
  6. Force a differential merge from the Advanced section under the Configure Agent Settings page.
  7. Run a chkdsk /r to fix and repair any bad disk sectors on the target server.

Advanced Solution

If all of the previous steps have failed, you can try an advanced solution.

This step involves editing the Windows registry, so proceed with extreme caution.

1. Go to the Windows menu, and type regedit into the search bar.

2. In the Registry Editor click the File menu, then click Export.

3. Save a backup of your registry.

4. Next, navigate to this key:

5. Delete the folders inside of this key, as shown in Figure 1.

Figure 1: Delete STC snapshot keys (click to enlarge)

If you receive a permissions error, try the following procedure:

  1. Download PsExec (external link).
  2. If regedit.exe is still open, close it.
  3. Open the command line cmd.exe logged in as an administrator.
  4. From the command line in the same directory as psexec.exe, run the following command:
    psexec.exe -hsi regedit.exe
  5. Try to remove this key again:
  6. If the key is still present, try:
    psexec -s reg delete HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum
    \STORAGE\STC_Snapshot\STC_Snapshot_[Snapshot Number]
    to remove each snapshot.

Repair agent communications with the protected system, and attempt the backup again.

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