In 30 years working with Unix, I've never encountered a situation where "defragmentation" was the answer. File system too full? Dozens of times. So, what usa

In 30 years working with Unix, I've never encountered a situation where "defragmentation" was the answer. File system too full? Dozens of times. So, what usage pattern am I avoiding to live such a charmed life? Anecdotally, I run a couple virtual machines on my laptop whose storage is on an external drive that sounds like Geiger counter at Fukushima Reactor 1 when the drive is busy. That is, when I've booted Windows 7. Not when I'm running anything under Windows, Windows just needs to be booted. When I'm running only a Linux VM, it drops to background level.