A few years ago I did technical field work for one of those outfits that farmed jobs out.
It was for a server decom at BofA. The job was simple. Find and verify the server, yank the drives and drill a hole and send a photo.
I got to the place and waited a little. A couple of staff people came out and we went to their server room. We hunted all over and could not find it.
They asked me to wait while they checked some more. Later they came out and admitted the server was shipped out a few weeks earlier. They signed off and I got paid anyway.
At the same time I was doing a refresh via a horrible FL based firm for HP/BofA (there was nothing else at all) and the PCs were to be wiped with GDisk. Any drive that failed had to be pulled and 4 holes drilled. It was supposed bank policy. I mentioned my experience and that one hole was good enough for a server, why not a cheap PC? I got yelled at for daring to ask.
Anyway I survived that nightmare and would rather starve than work for an outfit like the FL crowd.
I would say that unless what you have is so valuable that the NSA would use cyrogenic superconducting magnetic heads on it, a DOD-certified wipe will do it these days. There was a time (on <100 meg drives) when you could actually replace the disks themselves to a “good” drive and read them; then, there was a time (<10gigs, lets say) when you could replace disks and the PCB from a known good drive and read a bad disk. Both of these techniques could be done under “reasonably clean” conditions, even in your home. Now, the density is so high and the drive is setup with magic factory parameters that marry the disks, heads, mech, and PCB, super-secret proprietary firmware and algorithms that are probably known by 10 people at the factory, I’d say that recovery by mere mortals is just about impossible.
I’ve done the sorts of things described above twice in my career and grown men almost cried with joy.
I did work for a company and a good bit of it was for Chase bank. I’d get a call telling me that a server drive had failed. The company would courier in a new drive and a degaussing machine. I’d pull the old drive pop in the new one and tell the guy on the phone it was done. Then I would fire up the degausser and put the drive into it. Had to have a witness watch while the machine built up a charge and then “POP” and the drive was toast. I’d drop the old drive off at a FedEx on my way home. Loved those jobs at most 20 minutes of work and it paid 3 hours @ $30/hr.