yep, you can have raid 1 and raid 0 at the same time, it's called raid 10 (or 01 - for 4 drives it's the same - difference comes in at 6, 8 etc where you need to decide if you split the total capacity or add extra reddundancy). you need 4 drives of the same capacity, you end up with half of the total capacity running at 150-200% of the speed of a single drive. you stripe 2 pairs and mirror them
edit: or look at raid 5 and 6