Enable Phantom Device Cleanup

When VSS synchronized snapshots are created, the process requires that they be on-lined, mounted by the Windows host (to verify they were created and can be mounted successfully), un-mounted, and then off-lined on the array.

Mounting them on the Windows host causes a new Registry device entry to be created, even though that snapshot/device may never again be connected nor used. This is called a phantom device and takes up Registry space unnecessarily. A large number of phantom devices can cause problems when trying to log into a server.

The VSS requestor has a phantom device cleanup feature that periodically removes phantom devices from the Registry. This feature is controlled by Registry keys that were created when the HPE Storage Toolkit for Windows was installed on the Windows host.

IMPORTANT: If you are running Microsoft Exchange VSS Snapshots with verification, you could confirm that the phantom device removal registry keys are enabled. To get a list of all phantom devices, you can download the DevNodeClean utility from the Microsoft Download Center.
Caution:
Enabling phantom device cleanup removes all phantom devices from the Registry, not just phantom devices.

The cleaning of phantom devices should be enabled by default. If it is not, you can manually enable it by performing the following steps:

  1. Go to the Start menu, type regedit in the Search box and press Enter.
  2. In the User Access Control dialog box, click Yes.
  3. In the Registry tree, navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Nimble Storage\.
  4. Double-click the HKEY_LOCAL_MACHINE\SOFTWARE\Nimble Storage\CleanPhantomDevices key, change its value to 1, and click OK.
    Cleaning of phantom devices is now enabled.
  5. (Optional) View and change the other key values as required.
    Refer to the table below.
    Registry Key Meaning of Value Default Value
    HKEY_LOCAL_MACHINE\SOFTWARE\ Nimble Storage\CleanPhantomDevices 1 enables cleaning.

    0 disables cleaning.

    		1
    HKEY_LOCAL_MACHINE\SOFTWARE\Nimble Storage\CleanPhantomDevicesInterval The number of hours until the next cleaning. 24
    HKEY_LOCAL_MACHINE\SOFTWARE\Nimble Storage\CleanPhantomDevicesThreshold The number of phantom device entries allowed to accumulate before the next cleaning. 500
  6. Close the Registry window.