A long time ago, in a distant--err, before USB was popular, I used to use PATA hard drive caddies to back up my personal system. The caddies were like those used still in many data firms. Anyway, being short on money, I only had a few drives. I shut down my computer, slid a drive caddy in to the bay in the computer to do a backup. I turned on the computer--and heard the fire-cracker-like snap of exploding Chinese capacitors!

Aghast, I opened up the computer, and smelled the acrid stench of the burning money. Several of the capacitors on the power supply for the motherboard had exploded, spraying their electrolyte from their split can lids. Something else was wrong. I pulled the drive from the bay. There were components on the drive bay. A transistor was smoked. I pulled the drive from the caddy.

I built a new computer system. Setting my backup drive aside, I installed the old system drive as my secondary. After a reinstall, I did a drive check on the main system disk. It was corrupt! I tried the backup drive. It was completely dead!

Eventually, I was able to copy folders across, but on my old main drive, track-0 was physically damaged, preventing its reuse. In the end, I just barely kept my data. I didn't lose anything but money and time. My data was safe. So, the moral is: add hardware abstraction in the backup chain.