/Provider=ProviderNameOrId /For=ForVolumeSpec|/On=OnVolumeSpec - Displays all shadow copy storage associations on the system ...

%1 %2 [/Provider=ProviderNameOrId] [/For=ForVolumeSpec|/On=OnVolumeSpec]
    - Displays all shadow copy storage associations on the system for a 
    given provider.  Not all providers use  shadow storage.  You will 
    receive an error if it is not supported by your provider.  To list all 
    associations for a given volume, specify a ForVolumeSpec and no /On 
    option.  To list all associations on a given volume, specify a 
    OnVolumeSpec and no /For option.
    - The Provider ID can be obtained by using the List Providers command.
    When entering a Provider ID, it must be in the following format:
       {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} 
    where the X's are hexadecimal characters. 

    Example Usage: vssadmin List ShadowStorage 
                            /Provider={b5946137-7b9f-4925-af80-51abd60b20d5}
                            /On=C: