SIRIS, ALTO, and NAS: [Errno 22] STC Failure Occurred Mid-Transfer



This article discusses the cause and potential resolutions of the "Errno 22 Invalid Argument" ShadowSnap backup error.


  • ShadowSnap Agent


  • This error may be triggered during backup job initialization when the ShadowSnap software on a protected machine cannot properly access files shared through the Samba protocol by the Datto device to transfer backup job metadata.
  • This error may also occur on encrypted agents before data transfer is initiated over iSCSI.


Ensure that the ShadowSnap Agent is up to date. Find the latest ShadowSnap version information here

Restarting Services

Restart the following services on the protected machine:

  • ShadowProtect Service
  • StorageCraft ImageReady
  • StorageCraft Raw Agent
  • StorageCraft Shadow Copy Provider

Force a new backup. If the backup fails, continue with the steps below.

Reinstall the ShadowSnap Agent

  • If the preceding steps did not resolve the error, uninstall and reinstall the Shadow Snap agent on the server by following the process in the Reinstalling the ShadowSnap Software article.

If you are unable to resolve the issue using the steps in this article, please contact Datto Technical Support.

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