alt Hacker NewsI do some retro-computing every now and then and of these old drives that still work (about a 50% chance), when I format them assuming all sectors are good, they will inevitably report the same bad sectors as is on the label.
I don't really know why "bad sectors are still bad after 40 years" is so surprising to me, but there you go.
There's a step which "flashes" the magnetic structure on the disks during manufacturing which also allows drives to navigate the disk surface and "see" individual sectors. The bad sectors list from factory shows the points where this process has failed due to bad coating or other anomalies.
So they are not worn out sectors, they were bad (or not there) from the start. You can't rub them out, because there is not enough magnetic flux or material to store data at that address.