[EvanAnderson]

Here's my anecdote:

In 2006, while sitting at my desk playing a video on the Travelstar 40GB PATA drive in my Thinkpad T22, I held a single neodymium magnet (harvested from an old hard disk drive) about 6 inches from the left side of the unit (where the ~disk was located). The video froze, Windows XP blue-screened, and the hard disk drive started emitting a ~10Khz whine. I jerked my hand away from the PC immediately when the whine started

BIOS would no longer detect the disk on that machine, or any other I tried it on (on both USB-to-PATA and honest-to-goodness motherboard PATA controllers). The drive spun up but made a repeated ticking sound (I assume seeking back and forth looking for servo tracks).

I sent the drive to Kroll Ontrack (because, stupidly, I had billing data that wasn't backed-up on the drive). The report I received back indicated that 80% of the drive's sectors were unreadable.

As an aside: The data I was looking for was ASCII text and Kroll Ontrack was completely unhelpful in just sending me a bitstream image of the drive so I could grovel thru looking for data I needed. Being plain ASCII, their "file carving" tools didn't locate any of the data. (They sent me a "preview" of the data they'd located, and while it got lots of Microsoft Office-format files, it didn't have any ASCII text files). I offered them a 3x multiple of the rate they asked for file-level recovery to simply send me the bitstream image of the disk that they'd already made. They wouldn't do it, and wouldn't even let me pay to talk to somebody who understood what I was asking for. I ended up taking a major loss on the billing data I destroyed. I'll never recommend them to anybody.

I won't ever play with neodymium magnets around spinning rust media again either. I also had a major failure of my discipline re: backup at that time, too. The cobbler's children always go barefoot-- I was being too cavalier with my backup strategy (or lack thereof) and not treating my own data like I would a Customer's.

[ebg13]

> the hard disk drive started emitting a ~10Khz whine

This sounds like the head crashed and physically scraped the platter.

[egdod]

Sounds like a coincidence.

[EvanAnderson]

It does sound that way but, boy, it was eerily timed if it was.

[noonespecial]

I'd bet on related, but not what you thought. If I had to guess, I'd put my money on the magnet pulling some tiny metal bits into the control board and shorting it.

But one thing is for sure. OnTrack are dicks. Can confirm.

[mlyle]

Magnetic field falls off with inverse cube of distance once you're past the approximate size of the magnet. Not to mention that the drive itself is in a ferrous enclosure that provides a lot of shielding... the magnetic field you applied at 6 inches is approximately nothing.

[EvanAnderson]

I will definitely concede that I may have the 6" measurement wrong. Heck-- I may have actually put my hand right on the PC.

I stack running hard disk drives, all of which have large neodymium magnets inside them, in close proximity all the time with no ill effects. It makes no sense.

[FabHK]

Isn't it inverse square?

[mlyle]

No. Magnetic fields fall off as 1/d when d is small compared to the size of the magnet, progressing to 1/d^3 when d is large compared to the magnet. (E.g. weird edge case-- it's inversely proportional to distance from an infinitely long wire).

Electromagnetic radiation from point sources falls off as 1/d^2.

[FabHK]

Thanks a lot, both of you, learned something!

[egdod]

No, it’s a dipole moment instead of a monopole like electric charge. It goes as 1/r^3 in the far field.