When I looked at each drive, prior to any defrag work, they were all badly (very badly) fragmented.

I mentioned that I had been testing MyDefrag. According to its file-use map, it has successfully pooled all of the unused space and everything looked beautiful.

Two recordings later, I could see that the previously empty space had the two new files scattered all over it, not recorded in a nice linear fashion.

Fragmentation is quite apparent on these disks, however, I don't know if it's responsible or even a contributor to the problem I'm trying to remedy.