ReDuing my Deck, how to get old stain off?

Trying to save my deck for a couple more years. The previous owner looks like they just stained it a couple of times. Most of the Redish/brown stain is off the top, but their are spots. Mostly the sides of the deck still have the Redish Stain. Whats the best--easiest way to get this off? Do I just sand it off? that seems like thats going to take some time? Thanks