Whenever we are using SnapDrive the actual data is already on a LUN, i.e. on the filer, and for backup and mirrororing we use snapshot, snapmirror or snapvault technologies of Data ONTAP.
Since the data is already on the NetApp filer, SharePoint server doesn't need to copy any more data to filer.
When using mirroring data will be transferred from snapvault/snapmirror primary to secondary.