(And how yours could too)

Hard disk drives are a marvel of modern technology. With the ability to store the data of millions of books on a single hard drive, we’ve never been able to store more data at a lower price than we are now, and storage capacity is only going up while prices are only going down.

Even more amazing is the sheer complexity at work in a modern drive. The electrical, chemical, mechanical, computer, and magnetic engineering that must take place to develop a drive boggles the mind. A hard disk drive is truly a monument to modern technological achievement, and at only a couple hundred dollars a piece, most people have at least a handful in the various electrical devices around the house. From the TiVo to the family laptop to a camcorder to an iPod, hard drives are in more and more of devices we own.

With access to such cheap and powerful storage, it’s easy to overlook the fragility of modern disk storage — a lesson I learned the hard way.

In April of 2007 I received my first MacBook Pro from Apple. I was upgrading from a Powerbook G4 I had owned for 2 years, which had served me with only a couple of part failures (a bad battery and a hard drive that failed after a year). I took the new laptop home and started copying my data over. After two days I had it all setup. It was working wonderfully.

The Story

About 7 days after I brought it home I was checking my email with the computer on my lap when I heard a loud PING! cry out from behind the case. It certainly didn’t sound like a good noise, and the grinding that followed was even worse. My programs started to lock up and my computer would not restart. Dejected, I took the laptop to the Apple store, where a new hard drive was installed. Two days later I took the laptop back home and spent days reinstalling software. I was partially surprised that there was a failure so soon in the life of the laptop, but hard drives do die, and some die quickly.

Back up and running things were going well until 4 days later when it happened again. I was opening up the laptop when PING! went the computer. The repair kept me computerless for 5 days.

With the second failure I was skeptical that this computer would ever work right, and my doubts were validated when the THIRD drive failed after only another 10 days. Same as the first two, pinging, clicking, and grinding signaled the death of my laptop.

This time the technicians at the Apple store heard my cries and replaced the unit. I walked home with a brand new sealed in box laptop, glad that my hard drive problems were over.

At least for 5 days anyway.

That’s when it happened for the FOURTH time, on a completely new computer. I was surfing the web on a Saturday when I heard the ping of death. My heart stopped and I wondered if I was cursed.

When I took the laptop in they interrogated me for a while and eventually I left with a third brand new laptop (thank you Apple). As I was walking out of the store one of the questions a tech asked me rang again in my mind: ‘Did you expose the laptop to any strange magnetic fields?’ Of course my answer was ‘No.’ I couldn’t think of one. But then as I was leaving it occurred to me that my money clip wallet, which sits in my front pocket, does have a magnet. ‘But surely the laptop is shielded enough that couldn’t matter, could it?’ I wondered.

As I pondered more and more it seemed plausible. Every failure followed a session using the notebook on my lap. And as I read up on hard drive operation it seemed evident that if you could get a magnetic field to reach into the drive, you could definitely destroy it.

That’s when I realized that we had to do an experiment. What we discovered is terrifying: modern hard drives are much more fragile than we often consider, and exposure to even weak magnetic fields from close range could render a working drive absolutely useless.

The Experiment

While it was suggested to me to purchase a notebook hard drive, expose it to a magnetic field, and see if we could break it, then return it to the store of purchase, I thought that a bit risky, unethical, and potentially pricey. Instead, I opted to do some simple testing under the premise that if we can get a magnetic field into the drive operating area, then we can conclude that it is plausible that said magnetic field could ruin the drive. In other words, if the magnet can affect the drive at all, consider the drive dead.

Enter my old Hitachi 2.5′ notebook drive. It failed after one year of service, and I opened it up to see how it looked inside. Since the drive was already dead, it seemed like the best test subject.

Here is the plan:
1. Place iron filings onto disk surface.
2. Expose disk to magnets from varying distances.
3. Look for fluctuations in filings when exposed to fields.

First, we get some filings (filed from a piece of steel lying around) and dump them onto the drive. Now, we get out the money clip. First we’ll test with the magnet that I think might have killed my computers, then we’ll test with other sources if that yields no results.

The first test is startling. Not only does the field easily penetrate the bottom of the drive, it’s incredibly strong at the point of the top of the platter.

Moving the magnet away continues to yield disturbing results. We were able to make the pieces dance from a range of upwards of 5cm away!

And lest anyone ask, the top of the case has no obvious shielding properties.

Test Video

So What?

In plain english, any moderate magnetic field, from a speaker to a fridge magnet, could potentially disrupt the magnetic field of a hard drive, rendering it unreadable. Keeping all magnets of any kind far away from drives is vital.

The Conclusion

Hard disk drives are remarkable pieces of electronics. They incorporate a variety of technologies to store the valuable information that we create each day. But for all their amazing qualities, we find them to be startlingly fragile. If ever you were looking for evidence to reinforce the need to spread data around as you back it up, look no further than the above.

As for my laptops, most likely the money clip’s magnet interfered with the operation of my hard drives (all four of them), causing the destructive effects that I witnessed. While perhaps not perfectly confirmed, this myth is definitely plausible.

Appendix: Obvious Questions

Since undoubtedly someone will ask these questions, or argue that this test is unreasonable, here are my thoughts on the most likely rebuttals.

1. You didn’t prove the drive would actually die. You just moved metal filings.

True. But if a magnetic field can get into the platter region it can interfere with the fields already in place, and since both movement and data storage/retrieval rely on magnetic actuation, it is perfectly reasonable to conclude that the drive would be damaged in some way.

2. You didn’t take the laptop case into account.

Also true. However, in the case of my powerbook, the aluminum case provides little to zero effective shielding. The hard drive is located on the bottom of the case, in the front left corner. The effective distance in a real world scenario would be approximately 1cm. We were able to move filings at least 5cm away from the magnet.

3. Not all laptops have the drive in a similar location.

Also true. And that does matter. Had the drives been on the other side of the case they probably never would have been affected by the magnet in my pocket. But since the magnet could easily penetrate an entire plastic case from bottom to top, no modern unshielded laptop seems secure.

Additional Information

Flickr Photo Set
The Flickr set with all the photos taken for the experiment.