Thursday, February 4, 2010

How Not to Clean Data

PREFACE: Even if you don't have some familiarity with the inside of a hard drive, you'll probably still be troubled by this story from my past.  To answer the obvious questions that you'll have after the story: Yes, I really do have a legitimate degree in Electrical Engineering.  No, don't worry, I've never been employed in a way that uses that degree in a significant way to design or build any products that you might own.

I once had an old hard drive that started making a bit of a racket.  It didn't stop working right away, but I was concerned that there was something wrong with it.  I thought that maybe I could figure out what was wrong if I opened it up and poked around inside.  At that point I'd never seen the inside of a hard drive in real life.  So, I invested in my first set of star-point screw drivers and carefully disassembled the case of the hard drive.  Even after the screws were out, the metal cover stuck a bit.  It seemed like there was some kind of seal that had it closed, so I used a flat head screw driver to pry it open.

Wow.  Shiny.  Really clean.

I plugged the hard drive back in, while both the computer case and the hard drive case were open, and booted up the computer.  Cool.  It spins!  I watched it spin up, and the computer boot.  Everything working great.  That little moving arm is really neat, too.  It bounces back and forth really quickly!  So, I ran some programs on the computer and started listening for the noises that I thought were signifying an imminent disaster.  The hard drive just sounded rough.  Something like ball bearings worn down or the spindle just getting sticky.  Logically, I got out my WD-40, with the little red straw to make sure I could target the center of the spindle.

Squirt.... Squirt... drip, drip.

Well, let's see if this works for a while.  Maybe that was enough to quiet the drive down.

Things working fine.  Then the head did a seek and ran right through a drip of WD-40 and smeared across the platter.  Is that bad?  Then the actuator arm started thrashing back and forth, clicking hard against the center of the spindle and back against the outer wall of the case.  Clunk.  Clunk.  CLUNK.  Whirrrrr..rr...r....  Quiet.  Computer locked up.  Hard drive stopped.

Uh oh...

Maybe if I clean that WD-40 off of the platter it will work again?

So, I got out my trusty Goo Gone and a soft rag to remove the extra drips of WD-40 that were now smeared across the top platter of the hard drive.  Rub, rub.  Wipe.  Rub, rub.  Polish.  That looks pretty good.  Let's spin it back up and see.  W....h...i.rrrrrrrrrrr.  OK, that sounds pretty.... CLUNK.  Clunk.  Clunk.  Clunk.  Unplug the computer.

I worked on this for a couple of hours.  I used more Goo Gone.  I used alcohol -- both the rubbing kind to clean the platter and the drinking kind to calm my frustration.  In the end, I was able to get the drive spun up long enough to retrieve some files.  This was still an age when most of my working documents were on floppy disks, because I needed to carry those between different computers.  So, luckily, there was no important data lost.

I've been thinking a lot lately about how "broken" business processes impact data quality and data integrity -- thinking about the ways we look at trying to keep the data inside those disks clean and running smoothly.  Sometimes we look at things from a perspective that is too distant, with a too limited understanding of the context of the processes that we're examining, and act too quickly and too inexpertly without taking time to understand the nuances of the systems and business processes involved.  We do things that we think will help (implement governance processes and quality screens) and end up sending the system into a tailspin.  Things do recover from that dive, but not without a major investment in time and energy.


  1. nice story on DATA at a very low (H/W) level :)

  2. Fortunately users are not able to get at the hardware of an organisations data centres in the way you suggest. However, they may be able to introduce poor data etc. which, if you will pardon the analogy, is a little like allowing sections of your hard disk to 'rust'. This slow corrosion will start to affect the overall data quality. We need to manage the well intentioned, but misguided intentions of users.

    I have a similar tale to yours (but fortunately I am not the guilty party!) - a number of years ago I worked in a car parts factory where there were a number of power presses which used robotic arms to move parts through the press. This was clearly set up so that the arms moved the parts and retreated before the press came down, however, one enterprising foreman decided to manually push the relays to make the system work (he thought the system was not quite right) - Result was robotic arm went in, press came down on arm, foul language from my maintenance staff! Well intentioned, but misguided user intervention.

  3. Julian - I was afraid that your story was going to end with something much more gruesome. Glad it didn't!

    I agree that there's maintenance we need to do that will help keep the data itself from rusting. I also think that we have to be very careful to use the right tools (processes, governance, standards) for the right situation (culture, systems, environment). If someone starts tearing open the hard drive equivalent of some critical business process and spraying WD-40 all over the place it's likely to create more thrashing and clunking than value. Maybe the better option would have been switching to a solid state device or a graphite-based lubricant instead of WD-40.

    Maybe that metaphor is too much of a stretch.