/For=ForVolumeSpec /AutoRetry=MaxRetryMinutes - Creates a new shadow copy of ForVolumeSpec. ForVolumeSpec must be a local ...

%1 %2 /For=ForVolumeSpec [/AutoRetry=MaxRetryMinutes]
    - Creates a new shadow copy of ForVolumeSpec.  
    ForVolumeSpec must be a local volume drive letter or mount point.  If 
    MaxRetryMinutes is specified and there is another process creating a 
    shadow copy, vssadmin will continue to try to create the shadow copy for 
    MaxRetryMinutes minutes.

    Example Usage:  vssadmin Create Shadow /For=C: /AutoRetry=2