I'm not entirely certain return rates are a good indicator of failure rates. First, you only return a hard drive if it's under warranty so that gives you a 1-2

I'm not entirely certain return rates are a good indicator of failure rates. First, you only return a hard drive if it's under warranty so that gives you a 1-2 years window. Second, if you care about security, you don't really return hard drives. Once bought, unless you are certain everything is encrypted on them, the drives never leave the premises.