Erase that hard drive!

Hard Drive Platter Meets Pinball

Dumb little man (nice weblog, btw) has an entry reminding folks to actually erase the hard drives of their old computers.

He misses two key points.

First, secure erasing of hard drive contents is built into Mac OS X. Launch Disk Utility, click on the volume or drive you want to erase, then click on “security options…”. I just zero out all data, but you can be up to 35 times more paranoid than I am.

If you want to ditch a partitioned drive, I would suggest repartitioning the drive down to a single partition. This allows for a single erase-and-zero pass. Takes just as long but you don’t have to mess with it in the middle.

Secondly, don’t forget to erase the data on broken hard drives! Just because a drive no longer works does not mean the data is inaccessible! Often, carefully swapping the controller board on a drive is enough to restore it to working order long enough to pull off the data. Professional recovery services (and really careful hackers) can even swap the platters from a dead drive to a working drive to recover data!

Me? I take dead drives apart. They have amazingly powerful magnets inside, along with all kinds of very useful screws, washers, nuts, coils, and other fiddly bits.

The platters, obviously, contain the data and they should be destroyed. I run one of the magnets over them upon removal and then keep a stack of the platters around as they have proven to be incredibly useful! The platters have been used for everything as clamp pads for gluing stuff to spacers to level a table or work surface to being used by my son as part of a bug house.

Note that not all platters are made of metal! Some are made of glass! So, if you plan on smacking the platters with a hammer, be careful!!

Or, do what I did when I discovered this: Set up a high speed photog kit and drop a pinball on it!

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12 Responses to “Erase that hard drive!”

  1. Ahruman says:

    bbum (nice weblog, btw) has an entry linking to an entry reminding folks to actually erase the hard drives of their old computers, in which he references the Gutmann 35-pass secure delete algorithm.

    He misses a key point: according to Gutmann himself, “[the algorithm] will have no more effect
    than a simple scrubbing with random data. In fact performing the full 35-pass overwrite is pointless for any drive…”

  2. bbum says:

    That was the “35 times more paranoid than I am” statement. 🙂 Paranoia isn’t about practical or useful.

    But, thanks for the link.

  3. Charles says:

    I have an old VHS tape eraser, it runs off 120v AC current and its magnetic field is strong enough to lift heavy objects. The theory is that it uses alternating magnetic fields, so it’s better at erasing than a solid magnet. This should be the ultimate hard drive eraser, as it would erase the platters right through the metal case, and not just the data tracks, but also the servo tracks that tell the drive R/W head where to position itself. But I’ve never tried this, believe it or not, I’ve never thrown away a hard drive, they’re all still sitting in my closet!

  4. M$Worker says:

    you are an absolute idiot by the way. running a magnet over the plates will not do anything to your data. think about what you said…..”I run one of the magnets over them upon removal”, but yet INSIDE the hard drive, along side of the platters lays the MAGNETS…so obviously running the magnet over the platters wont effect them at all. hopefully you do some research or know what you are talking about before you go chattering.

  5. bbum (waiting for panic'd machine to reboot) says:


    First, the incredibly powerful magnets off to the sides of the platters are extremely precisely engineered to shape the magnetic field such that it is effectively contained. Most are in the form of a little sandwich and, when assembled, there is very little field leakage. So little that the magnet assembly will typically not stick to a refrigerator whereas the isolated magnets not only stick, but are hard to pull off.

    Secondly, hard drives and floppies are not as susceptible to magnetic fields as you might think. The presence of a weak and relatively constant field won’t erase data. A moving field is key and taking a really powerful fixed magnet and waving it over the surface works quite well. Degaussers work even better as they use AC current to produce a constantly moving — collapsing and expanding, actually– magnetic field that erases the data.

    If I really care, I destroy the platters (or use them for other purposes immediately which, invariably, results in them being bent and scratched). Otherwise, the above will erase the data plenty well enough that only a seriously interested party with a pretty hefty budget would be able to restore the data.

    Hell, you are talking about drive platters that have been removed from their clean room hard drive environment. That, alone, effectively makes the data inaccessible to all but the very most interested parties.

    Since I don’t browse kiddie porn, run a crime ring, or have bazillions of dollars in offshore bank accounts, I’m pretty damned sure that said “most interested parties” would find a lot more attractive targets than me.

    Oh, finally, if you are going to be calling people idiots, get a clue first. Calling someone an idiot when you are, in fact, wrong doesn’t reflect well upon you.

  6. gojohnnygo says:


  7. bbum says:

    Good song and a good way of erasing a drive. Tends to powder those useful rare earth magnets, though.

  8. Fascination Place » Old Computer Junk says:

    […] I bought back in 2001. It’s now been replaced twice and is not used at all. I’m being 7 times more paranoid than bbum and doing a 7-pass zeroing erase on the drive. Once that’s done, I’m just going to […]

  9. bbum’s weblog-o-mat » Blog Archive » Magnetic Finger: A Sixth Sense says:

    […] chat today and, somehow, the conversation turned to magnets. Maybe it was because I got called a complete idiot by the clue […]

  10. John C. Randolph says:

    Will it BLEND?

    Saves time, and it’s far more entertaining. 😉


  11. ratty says:

    To day I have 8 commercial drives to wipe, I elected to swirl a “very” powerful bar magnet around the disk area 10 times in each direction and test the result. Magnet 60mm x18mm x 140mm. strong enough tho pick up a steel garden spade. ( sorry dont have a gaus meter).
    The magnets from inside a hard drive would be strong enough, they are massivly strong for there size.
    The partitions and data were gone, but the drives remain usable after partitioning and formating.
    It is possible that bits of data remain and could be recovered but they would be scrambled fragments and the cost of recovering them would be prohibitive to all but the crimanaly obsessed or the police ferensic team desperate for a clue.
    In the extreme data recovery world, electrons microscopes can be used can on bent fragments of disk.
    If you can conceive of a strong magnetic field and tiny magnetic particales being pulled around 360 degrees several times then you understand the process I use.
    Its only a matter of magnetic strength, proximity and motion.
    The true paranoid need to grind the platters into powder, the rest of us need to use common sense and try not to waste recourses by recycling drives.

  12. daniel says:

    i agree with Mr. sledgehammer

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