A few years back I underwent an effort to image a bunch of old 3.5” floppies I had from when I was a kid. I used KryoFlux, and had a close to 100% success rate (eventually)

Some things I learned:

1. Different drives could read different sectors. I am not exactly sure why, but some disks would show bad sectors when read from one drive, but would have a different set of bad sectors when read from a different one. I had 5-6 different drives I was using (I bought a bunch of used drives, they are pulled from old hardware and resold). I think it likely has something to do with the heads being slightly misaligned or something, so they would struggle with different sectors.

What I would do is scan a disk with one drive, and if I found any bad sectors, I would re-scan with a different drive. I would repeat this process until I had at least one good scan of each sector. I would then pull the missing sectors in one scan from a scan that succeeded on that sector, and would patch together an entire image.

2. I didn’t realize how varied the formats are for disks I had. I remember single vs double sided, but there were quite a few other variations I found in my collection.

3. If you hang out with computer nerds of a certain age, you are going to be surprised by how many of them still have a collection of old floppies that they can’t access anymore. I had so many requests to help archive many different collections!