enforcedcrowd, are you experiencing any symptoms of a failing drive? The sound sounds like when the drive is been accessed. However, it is not a bad idea to have a good back up plan in place just in case.
Basically you want:
3 copies of any data you don't want to lose.
2 different mediums it's stored on (so 2 different drives in your computer, for example).
1 copy kept offsite, to prevent against disaster. Let's say an asteroid strikes your house or a tornado hits it, you want a copy somewhere else so you can retrieve it.
USB drives can be used for an extra copy at your main workstation and/or as a copy you back up to, then disconnect and keep at another location.