A VADP backup cannot create a VM snapshot and fails with the error: "StartBackupSession failed. error: Create snapshot task failed: The operation has been disabled by the guest operating system (VixDiskLib_PrepareForAccess returned error code: 20005) An error occurred while saving the snapshot: Exceeded the maximum number of permitted snapshots. Failed OpenListing for..."



The special parameter "snapshot.maxSnapshots " for a Virtual Machine is configured to NOT allow a snapshot creation.



To re-configure the special parameter "snapshot.maxSnapshots " for a Virtual Machine to allow snapshots creation, please use following steps:

  1. Shut down the Virtual Machine.
  2. Right-click on the Virtual Machine in the vSphere Client and click Edit Settings.
  3. Click the VM Options tab, click on Advanced, then select the Configuration Parameters option.
  4. Search for a string name called snapshot.maxSnapshots and increase it's value.
  5. Click OK to save the changes.
  6. Power on the virtual machine and run the VADP backup.

Please also refer to the VMware KB#1031280.