I'm building a raised bed(s) (my first) and I'm using redwood because I heard that it's like cedar and rot resistant. Should I also stain it with anything to further help it last? If so, what would be a good stain that wouldn't effect the veggies?

Also, how high? I was planning on 6 inch tall sides but is it worth going to 12 inches as it will basically double the costs? The two beds I'm building this year are for asparagus and rhubarb. Next year the vegetable garden.

~Yago