What is the universal (world wide) understanding behind degaussing harddisks?

[David Fletcher]

On Tue, 2018-04-03 at 11:06 -0500, Tommy Trussell wrote:
> In my (very limited) experience, one can use an "old fashioned" tape
> "degausser" aka "demagnetizer" on a hard disk, but after doing so the
> drive is generally "toast." (I suspect the head mechanism gets
> damaged by the process, and the motors probably don't take kindly to
> being degaussed either.)

There's a pair of impressively powerful little magnets that I believe
are part of the head positioning mechanism, so if a drive were to be
totally degaussed the drive would indeed be toast.

BTW I once tried to degauss some DAT tapes with all sorts of gadgets,
to re-use them in another drive (as I recall the drives appear to write
their own "signature" on the tape so they won't work in another one so
no use for disaster recovery after e.g. a fire). The only machine that
did it was one that I found on an industrial estate where they
manufactured large custom magnets, the final stage being to put them in
this machine that as I recall dumped a large capacitor bank into an
electromagnet. That wiped the DAT tapes. I strongly suspect that the
magnetic domains on hard drives, tapes and things are not as delicate
as some would have us believe.

Dave