After moving to my new servers, I am testing/wiping some old HDDs. I have a couple that have failed SMART tests but they still pass physical tests, so I wiped them & will give them away with appropriate caveats. Single pass wipe, (all 0s) to a 1TB disk usually takes 2-3hrs. Except 1, which took an hour to get an ETA, which was originally 28h. It has been running for an indicated 21h, with 9:10 remaining. So I think that one actually is toast, but at least I know it's not holding any data.