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.

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

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

   Posted by MrsDoF  on  10/17/05  at  08:55 PM

2. Here is a user point of view for Hard Disk Crash

   

   Posted by Abster  on  10/18/05  at  02:18 PM

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

   Posted by The Bo$$  on  10/18/05  at  05:40 PM

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.

   Posted by george.w  on  10/18/05  at  09:29 PM

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…

   Posted by Buridan  on  10/19/05  at  03:06 PM

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

   Posted by oldgreek  on  10/26/05  at  11:35 AM

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.

   Posted by Mark  on  10/28/05  at  06:01 AM

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

   Posted by The Bo$$  on  10/31/05  at  11:30 PM

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!) 

   Posted by george.w  on  11/01/05  at  09:06 AM

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

    

    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.

    Posted by george.w  on  11/01/05  at  03:59 PM

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.

    Posted by Logan Neidlinger  on  07/16/07  at  11:24 PM

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

    Posted by steve  on  10/30/08  at  10:01 AM

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.

    Posted by Igor Musta  on  08/11/09  at  02:08 AM

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.

    Posted by Pieter Kuiper  on  08/24/09  at  02:05 AM

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.

    Posted by George  on  08/30/09  at  04:52 AM

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.

    Posted by George  on  09/01/09  at  09:07 AM

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.

    Posted by Pieter Kuiper  on  09/02/09  at  04:43 AM

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.

    Posted by George  on  09/02/09  at  06:59 AM

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.

    Posted by Pieter Kuiper  on  09/02/09  at  09:51 AM

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.

    Posted by George  on  09/11/09  at  06:54 AM

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Decrepitude

A few selected articles from the last few years. Feel free to nominate others because really, I can't remember what all I've written.

9/11: five years on
Story from a picture
The Authority Gradient
If our lives are to have any meaning
What was lost
Cold and broken alleluia
Mary Mallon: being evil vs. being an evil
Artifacts of the long-gone man
A message to Republicans
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Because nature isn't waiting for us to wise up

Creative Commons stuff

I tried to figure out the Creative Commons and Wikimedia stuff but it was like doing your taxes in another language. Short version: it's OK if you copy my stuff as long as you give attribution and you're willing to share what you make of it with others. Here's the little logo:

This work by George Wiman is licensed under a Creative Commons Attribution-Share Alike 3.0 United States License.