[EvanAnderson]

I will definitely concede that the 6" number may be an incorrect memory. It certainly may have been closer, but it wasn't right on top of the unit.

If it was a coincidence it was certainly well-timed. I don't have the Thinkpad anymore, but I do still have some 2.5" PATA drives. It might be interesting to test this and make a video.

Here's a picture of the magnet in question (it holds stuff to my refrigerator now), w/ a penny for scale: http://mx02.wellbury.com/misc/20171203-Magnet_of_doom.jpg

This magnet was pulled from a Micropolis 9GB SCA-II 3.5" low-profile drive dating from roughly 1998 (I had a crap-ton of these drives and, as they died, I pulled their magnets, so I have a bunch of these). These particular magnets will stick to each other thru my 3" thick butcher block table. They are physically larger (substantially thicker) than the ones I've pulled from newer drives.

Edit:

I assume that the data and servo tracks written to the drive are done so in the presence of the magnetic flux of the magnets supporting the voice coil. I always just assumed that adding a substantial new source of magnetic flux (the magnet in my hand) either induced a current or magnetized some component in the drive.

[syshum]

>> They are physically larger (substantially thicker) than the ones I've pulled from newer drives.

Not really, they look very close in size to current Enterprise Drives (https://imgur.com/2HjuuKM), Of course I have removed the Metal backing plate from mine

Now consumer drives do have smaller magnets (that is one way to save cost)

Here is a photo of the 4 styles of magnets I still personally have, the smaller magnets are either out of consumer drives and 2.5in drives manufactured in the last 7 years https://imgur.com/59XjVPm

And just for fun a small assortment of my collection because why not

https://imgur.com/bW6ycRI

[EvanAnderson]

I've only had the opportunity to tear down a few consumer drives in the last few years. I haven't seen inside an enterprise-class drive in a few years. (I've stopped dealing with hardware directly for my Customers, and I haven't purchased much hardware for personal use over the last few years.)

I've found scavenged hard drive magnets to be very useful for odd jobs. One served several years holding up the fallen head-liner over the drivers seat in one of my crappier cars.