This might sound funny, but if you have 5 disks in a raid, how do you identify the faulty drive (physically) in your NAS box?

Good Day all, I am new to FreeNAS, an OK server person and overall general techie...now that you know a little about my skill set here is some hardware info, I currently am attempting to reduce the 'size' of my setup (hardware). My current setup is basically the following: Sitting in a norco...