New versions of SnapDrive and MPIO that officially support Windows 2012 R2 have been released. See the URL’s below.

Data ONTAP DSM 4.1 for Windows MPIO
http://support.netapp.com/NOW/download/software/mpio_win/4.1/

SnapDrive 7.0.2 for Windows
http://support.netapp.com/NOW/download/software/snapdrive_win/7.0.2/