I needed a quick and dirty way to make a specific hard drive LED blink so that I could identify which drive to replace. I stumbled across this post that worked well for me.

The simple trick is to run smartctl in a while loop. Something about smartctl makes the drive light blink differently than using dd, which is what I was using previously. smartctl is what finally allowed me to identify the drive. Here is the command:

while true; do smartctl -a /dev/<device>; done

The command will run forever until you Ctrl + C. It make the LED blink rather obviously, which made things much easier.