503 Fatal I/O error (-31 A device attached to the system is not functioning).

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User receives a DD-MM-YYYY HH:MM:SS sbfile 503 Fatal I/O error on (Drive):\(File Name) offset 00000000 on (write/read) (-31 A device attached to the system is not functioning.)


This error is reported by Microsoft Windows to ShadowProtect. This error happens when the system has reported a communication problem either while trying to read information from the drive being backed up, or while trying to write data to the drive the backup is being saved to. The problem can be caused both by faulty hardware as well as by file system issues.

Other evidence of these errors can also be found in your System Event Log as NTFS, FTDISK, and DISK errors. For information on how to view your System Event Log, please refer to the How to view and export Event Logs KB article.


For information on these errors please reference Microsoft KB Articles: 885688 and 244780

It is recommended that you run CHKDSK /r on the drive that is experiencing the problem. If the error is on Read, it is the drive that is being backed up. If the error is on Write, it will be the drive you are saving the backup to. NOTE: CHKDSK does not always find or repair these errors. Much of the time it is necessary to obtain a better diagnostic repair utility from the Hard Drive Manufacturer.

Below is a list of links to diagnostic/repair utilities from many of the major hard drive manufacturers.
Western Digital/WD
Toshiba - Does not have a diagnotic utility.

Sometimes none of these utilities are capable of repairing your hard drive. In these situations, the hard drive is not stable enough for ShadowProtect to get a good image of it. If ShadowProtect cannot get a good image, it usually means that even if it could, the data would be corrupted to the point that the data would not be restorable. In these situations it is advised that you copy your important information from the drive manually and in small quantities. Copy large amounts of data or a multitude of files at a time on a failing hard drive will usually fail and leave a user unsure of what was and was not copied.

After the important user data has been transfered from the drive, you will either need to contact your computer manufacturer or a third party to obtain a replacement hard drive.

Additional Information:

This error has been experienced by users using Norton Protection Center. On Vista Home Basic. It may also occur with other anti virus, firewall or Intrusion Prevention software, on other environments. To confirm this, shut down or stop the Norton ( or other ) Firewall or Intrusion Prevention service. Start the Shadow Protect image backup again and confirm that it completed OK. If it fails, please check the log file, as it may have failed for reasons other than this error. If this error is not repeated in the log file, then you have confirmed that the Firewall or Intrusion Prevention service is the issue. It is expected that you would like to leave this service enabled. For the Norton Protection Center software, this can be done as detailed below. For other systems consult relevant documentation to achieve a similar functionality.

In Norton Internet Security:

      1. Open the Norton Protection Center
      2. Select tab [Norton Internet Security]
      3. Select [Settings]
      4. Select Web Browsing [Intrusion Prevention]
      5. Select [Configure]
      6. Select Signature Exclusions [Exclusions]
      7. In the list un-check the box for MS RPCSS Attack (2)
      8. Select [OK] as many times as required and close the Norton Protection Center window.
      9. Perform another Image backup and confirm that it was successful. If not please contact our tech support service.

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