There is no such thing as "snapshot of LUN" - you always take snapshot of a volume. Snapdrive just resolves volume name from LUN name and hides from you gory details. Additionally on Windows it makes filesystem sync; I am not sure whether it does it on Linux; AFAIK not.
So to create crash-consistent snapshot of a LUN just create snapshot of a volume containing this LUN.
Re: How to take Snapshot of a LUN through NetApp API's