ools

Hi all,
I've been reading through this thread for several days, and I love all the ideas and tips. I recently rerolled to resto from feral (long story), and I'm trying to improve my PvP knowledge. I suspect I'm not understanding resist mechanics fully, and I couldn't find an answer to this question in the thread.

It was my understanding that resistance over 0 would grant the player a chance for partial resists. I did not think resistance would affect full resists. For cyclone, it's either full resist or full effect. Assuming I have 3% spell hit, and all I care about is whether my cyclone gets resisted, does spell penetration help me? Can you please help me understand how?

Thanks!
-Ools