If police know about the drugs in your house, then a raid is more than possible!
Jokes aside. You don't want to raid 1 your ssd with a HDD, your SSD will then run at the speed of the HDD, (if it's even possible to raid it / find a HDD the same size as a SSD)
RAID is NOT a backup solution, it is a redundancy solution, big difference! If you want to backup what's on your SSD, I suggest using something like rsync