All that matters is your tolerance to risk. RAID 1 shows you are attempting to reduce data loss. The final issue to solve is where is the backup. Some continue to try to avoid the backup issue by implementing RAID 1. Later they discover that RAID 1 wasn't much a parachute. The trojan wipes both drives at the same time!
Ok I have 2x1Tb drives in raid 1, should I have my OS and apps on the raid drives or would it be better to have them on their own seperate drive.