Recovering data from a damaged hard drive

2008-12-30 04:32 by Ian

Imagine that I have an assortment of glass items (files). This list ranges from car windshields to dishes to lenses. Anything that is made of nothing but glass.

I have a 40 gallon garbage can (the hard drive).
When a computer stores your data, it would be like you handing your glass item to me. I would then proceed to smash it to bits and throw the destroyed item into the garbage can. I do this because storing it all smashed up takes up less space than storing it in one piece. Not only that, but it doesn’t matter what the item was. If it was made of glass, I can store it for you.

Now eventually, you are going to want your dishes back. So you come and ask me for it.
I then go find each piece of glass that went into your dishes. I then hold them together and press just the right way and pop. I hand you your glassware in exactly the same state that you handed it to me in. Every atom accounted for. Every lipstick mark.

The only thing that enables me to do this phenomenal trick is this: I number each chunk of broken glass and record where each fell. I record this information in a notebook and when I leave my shift for the day (I have a really awful job), I put the notebook in a very specific place in the garbage can.

Well, the notebook inside of your hard drive caught fire.

Charred scraps of it are still present and legible. But information was definitely lost. Your chandelier and television tube are right there in front of us. But without that damn notebook, it all looks like shattered glass. The more of the notebook that survived, the more of your glassware we can retrieve. So, however damaged the notebook is, we don’t care at this point. We take all the information we can and start looking for patterns to fill in the rest:
Maybe this specific piece of glassware was tinted green…
That item had a frilly edge…
When I hold this collection of glass chunks up to my eye, my vision improves…

...and such is the task of data recovery. There’s a reason data doctors can charge people $2000 to put as much of their glassware back together as possible. Hardly anyone knows how to do it.

I’m still in the process of figuring out how badly burned the notebook is. But at this point, it is looking pretty bleak. Fortunately, this is an endeavor where creativity and math cross. So there is a chance of some success.