Home > Geeky, hardware > Hard Drive Crash

Hard Drive Crash

October 17, 2005

Update: scroll down to comment #10 for a better picture of this hard drive.  Feel free to copy and use the picture.

“Can you get my files back?”

“No.”

Inside your desktop computer is a data-storage device called a “hard drive”, so named because it stores data on a spinning aluminum platter (as contrasted with the mylar data-storage surface of a “floppy disk”).  These platters spin 60 times per second or faster and are mirror-shiny, perfectly flat as a telescope mirror is perfectly curved.  They are usually electroplated with a cobalt alloy because aluminum cannot record magnetic impulses.

The data is written onto the platter by a tiny electromagnet that floats a couple millionths of an inch above the platter at the end of a head actuator, which positions the head above the precise location of the magnetic imprints.  This electromagnet is called a “Read/Write head”.  Normally it never touches the platter when the drive is turning.

When drives fail, they usually make a clicking noise known as the “Click Of Death” as the drive controller (the circuit that steers the actuator arm) seeks but cannot find track zero.  Another failure mode is a “Drive Crash”, where the head literally crashes into the moving platter, grinding away the surface (and your data).

This drive made a horrible screeching noise in operation as the R/W head ground its way into the aluminum.  Usually the platter surface is intact except for the inner-most track (track “0”), but in this drive there was a bonus; the head kept seeking after the crash occurred, grinding up the whole surface of the disk.  The drive was full of aluminum powder.


Notes:

By the way, if you can get ahold of an old hard drive, take it apart.  They’re very interesting devices.  The platters are so perfect you can reflect a visible spot of sunlight a couple blocks away.  Hard drives contain the strongest magnets most people will ever see – usually a neodymium alloy with cobalt, iron, and/or samarium. (and strong enough to stick a magazine to your refrigerator).  The ring-shaped spacers between stacked platters are (like the platters themselves) machined to absurdly fine tolerances – for some reason it is inspiring to handle such precise parts.

Shown in this picture is the interior of a normal hard drive.  Upper-center is the data storage platter, which rotates around the main spindle.  Extending into the platter area from the lower right is the actuator arm.  At the upper tip of the arm is the read-write head.  At lower-right is the “voice-coil” portion of the actuator (where the super-strong magnets are located), which moves the arm around the actuator spindle to locate the read-write head on the platter surface.  Not shown is the drive motor and control circuit, as they are on the other side of the drive.

Categories: Geeky, hardware
  1. October 17, 2005 at 20:55 | #1

    Great close-up picture of the Read/Write head.

    Plus, that has got to be the coolest self-portrait shot ever.

  2. Abster
    October 18, 2005 at 14:18 | #2

    Here is a user point of view for Hard Disk Crash

    1951Hard_Drive_Crash10980_5708058.JPG

  3. October 18, 2005 at 17:40 | #3

    You can use Gmail to back up your hard drive, too.

  4. October 18, 2005 at 21:29 | #4

    Gmail backup – cooool!  Luckily this particular drive (which crashed about two years ago and I just ran across it while cleaning up my office) was a lab machine and the user only lost a few files.

    The biggest problem most users have is not lack of backup options but lack of understanding of file management.  They scarcely understand what a “file” is, let alone where their files are or what “backing them up” would entail – as Abster’s cartoon aptly shows.

    I hope by publishing pictures and explanations it may help more people understand what a hard drive is and that they can fail.

  5. October 19, 2005 at 15:06 | #5

    Nice explanation and description of hard drive mechanics. I’ve been lucky with only one “click of death” event. Now that I’ve said it, one of my hard drives will undoubtedly crash tomorrow…

  6. oldgreek
    October 26, 2005 at 11:35 | #6

    I have a question. On the bottom of this page is some info: times viewed, page rendering speed. Those are self-explanatory. What does the last bit indicate? In this case being “38 queries executed”
    oldgreek-visitor from SEB

  7. Mark
    October 28, 2005 at 06:01 | #7

    Here’s an old classic on the subject

    Yesterday—The Backup Song
    Yesterday,
    All those backups seemed a waste of pay.
    Now my database has gone away.
    Oh I believe in yesterday.
    Suddenly,
    There’s not half the files there used to be,
    And there’s a milestone hanging over me
    The system crashed so suddenly.
    I pushed something wrong
    What it was I could not say.
    Now all my data’s gone
    and I long for yesterday-ay-ay-ay.
    Yesterday,
    The need for back-ups seemed so far away.
    I knew my data was all here to stay,
    Now I believe in yesterday.

  8. October 31, 2005 at 23:30 | #8

    Do you mind if I upload this image to Wikimedia, DOF?

  9. November 1, 2005 at 09:06 | #9

    OldGreek, this is a case of “Les is more” as in… Les Jenkins over at SEB could answer that question better than I could.  As I understand Expression Engine, the page does not exist until you call for it, and then it is assembled from a database; hence the “38 queries executed”. 

    Buridan; good luck!  I don’t think hard drives are listening to us, so you probably didn’t jinx it. (OK, I’m whistling in the dark!)

    Mark – good one!  I’m putting that one in my next “email from the geek” to our department; thanks.

    Bo$$ – you’re welcome to the picture (but now I wish I’d done a better job of making it!)  :red:

  10. November 1, 2005 at 15:59 | #10

    I looked in my culch-pile, and still have that drive.  Here is another attempt at a picture:

    hard-drive-badcrash.jpg width=425 height=340

    I have passed this drive around a couple classrooms while teaching computer support.  Students like to see the actual thing rather than hear me yap about it.

  11. Logan Neidlinger
    July 16, 2007 at 23:24 | #11

    I opened up a old 883mb hard drive from a pentium 1 computer that crashed, there was a ring around the edge, and there was a lot of aluminum powder in there. The drive was making the click of death, and was vibrating like crazy.

  12. October 30, 2008 at 10:01 | #12

    its actually great to find out how things worked, most of us just simply turn our computers on, its actually nice to know how one works

  13. August 11, 2009 at 02:08 | #13

    If your computer won’t boot, don’t panic. just sit back, take a few deep breaths, and relax. The blank screen or the failure to boot up does not always mean you’ve a crashed hard disk. Today’s hard disks surprisingly outlast all other key computer components, and using system utilities unnecessarily also taking out and reinstalling the hardwares can certainly do more harm than good.

  14. August 24, 2009 at 02:05 | #14

    Hi George, above you gave permission to use your photo on wikimedia, and it is in use in several wikipedia articles. However, this is not quite enough for storage on wikimedia commons. So now there is a deletion request. What is needed to keep is a free licence that allows anybody to use or to modify your image, also for commercial purposes. Without explicitly asking you again, someone had put a creative commons license on it. Please tell if you agree with that (or with a different free license) or not.

  15. August 30, 2009 at 04:52 | #15

    Hi Pieter, sorry I missed your comment some days ago.  My Gmail account was skipping comments from my blog. 

    Yes, it is fine to use the picture.  I will look more closely at CC licensing for all the images on my blog – it is OK to copy them and use them though of course I prefer attribution.

  16. September 1, 2009 at 09:07 | #16

    Pieter, I have added a Creative Commons link on my sidebar, giving explicit license to use photos from my site.  I tried editing the entry at Wikimedia but couldn’t figure out how to do it.  Can you update?

    Also be sure to check out the picture I uploaded in comment number 10, a better image of that drive.

  17. September 2, 2009 at 04:43 | #17

    George, thank you for your answer. Although the problem remains – commons does not host images that are limited to non-commercial use. For this image to remain on commons, they require a statement that it is ok to use and modify this image for any purpose, including commercial use. If you do not want to make such a statement, that is perfectly fine of course – not many people want to give their work away for others to make a profit on. I am sorry that all this legal stuff with all the different options is such a pain.

  18. September 2, 2009 at 06:59 | #18

    OK, let me think about that one for a day.  I may change the license.  Not as if I’m making a profit off my blog.

    We’re having this “information wants to be free” discussion in our college, with some professors afraid that some big secret will leak out if their lectures are posted on the web.

  19. September 2, 2009 at 09:51 | #19

    It does not need to be the same for all images. You could have more restrictive licenses as the default, and still release selected ones on a free license.

  20. September 11, 2009 at 06:54 | #20

    Thanks but I know myself too well to think I’m going to apply differential licenses.  Decisions take time and energy so I like to make them all-encompassing when i can. 

    Sorry for late reply; for some reason, your comment got snagged by the spam filter.  I’ve been getting a LOT of spam lately but luckily the filter has been getting most of it.  False positives are the downside.

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