So I guess this isn't an OS-specific question, but I don't have a lot of experience testing hard drives in Ubuntu. My concern is that my external backup drive (connected via eSATA) has started sporadically making a click of death sound. However, it's not all the time, and the drive seems to function completely normally otherwise. It passes the SMART tests; there are a few red flags in the attributes section (which, notably, my other drives do not), but nothing even close to the failure threshold. If I catch it when it's clicking and access the drive, it works just fine and in fact stops clicking on access. I have it doing nightly backups and haven't gotten any errors in the logs.
Obviously the safest course of action is always just to replace the drive. But the drive's less than 2 years old, WD Black (which I've had nothing but great experiences with) in an external fan-cooled enclosure. I've encountered the click of death after failure, as well as chirping on access pre-failure, but never this kind of clicking without any errors in reading from or writing to the drive. Just wanted to get some feedback before jumping straight to a replacement.