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Troubleshooting inSync client backup failure with Volsnap error: "Shadow Copy on volume C: was cancelled because of an IO/error"

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Disclaimer: The steps mentioned in this article should be performed only after consulting your System Admin. VSS is an OS component, hence it is advisable to consult Microsoft or your system admin before proceeding.


This article explains the procedure to troubleshoot inSync client backup failure with Volsnap error.


  1. inSync Administrators will get an alert about the failed backup of the inSync client(Alerts must be configured).
  2. You can see the Windows System Event log with the error ID 14 and the message as following:

      Shadow Copy on volume C: was canceled because of an IO/error.


  • This issue mostly occurs when there is any disk encryption software installed on the client machine. For example - Symantec whole disk encryption, Truecript, or other products. For some reason these softwares prohibit the creation of new Shadow copies.
  • Following are the reasons and resolution for event ID 14. 

1. A disk I/O error occurred while performing the copy-on-write operation.There is a bad block on the disk that contains the volume where the Diff Area is stored. Check event logs for any NTFS or disk issues.
Resolution : Using chkdsk /r, check for errors on the volume where the Diff Area is stored and on the original volume.

2. The Diff Area is not large enough to store the shadow copies.
Resolution : We need to increase the DIFF area size. Given below is the command.

vssadmin resize shadowstorage /for=<forvolumespec> /on=<onvolumespec> [/maxsize=<maxsizespec>]

Reference link:

3. The disk I/O or system load is so large that the Diff Area is not able increase in size fast enough.

 Resolution : Determine if the computer is low on system resources like CPU resources, disk I/O performance, or memory. To identify what is causing the system to be low on resources, you can generate a System Diagnostics Report using Reliability and Performance Monitor, or you can use Resource Monitor to determine, in real- time, which applications or services are utilizing too many system resources.

Reference link :



  1. Confirm if there is System error event ID 14 for Volsnap on the client machine.
  2. Check if any disk encryption software is installed.
  3. Disable or engage the disk encryption vendor and fix the Volsnap issue.
  4. Try inSync client backup again.

Note: After fixing the Volsnap issue, if the inSync client still fails to backup with backup failed error message, contact Druva Technical Support.

Applies To

inSync client installed on Windows XP, Vista, 7, 8, and 10.