Re: destorying the hard drive
On 24 Mar 2008 03:14:51 GMT, thanatoid <waiting@the.exit.invalid> put
finger to keyboard and composed:
>"Bill in Co." <not_really_here@earthlink.net> wrote in
>news:ux0Q6QSjIHA.5412@TK2MSFTNGP02.phx.gbl:
>
>> I certainly would expect that writing pseudorandom, or even
>> identical, bytes to each and every sector on the disk would
>> make it nigh impossible to recover anything, - IF that
>> laboriously slow procedure was invoked. How it could
>> possibly be otherwise makes little sense to me - unless we
>> operate under the assumption that the electromagnetic
>> writes are somewhat incomplete (that is, the magnetic
>> domains on the disk are not fully reversed (or realigned)
>> completely, but still have some very small residual
>> leftover effects (i.e. retentivity) from a previous write
>> operation). (I'm an EE, but I'm just making some basic
>> assumptions here!).
>
>This idea - as *fact* - was presented in a thread with the same
>subject (I wonder just HOW many of those there have been by now)
>by someone a few years ago. He claimed a "residue" of whatever
>is written to a HD /REMAINS/ even if you write over it a bunch
>of times - something like: new drive, zero-formatted - 100%
>magnetic signal retention, second write in the same sector -
>95%, third 90%, etc. I pointed out that simple logic would
>dictate that if anything like this was true, all drives would
>fail within a few weeks of being installed. There was no reply.
Yeah, that makes sense. At the risk of taking this subject off topic,
it may be interesting to note that "hifi" VCRs record audio and video
on the same track, albeit with separate audio and video heads. The
audio information is buried deep under the video information, and is
recorded with a 30 degree azimuth angle to minimise crosstalk.
Although it's a completely different technology, and it has no
relevance to HDDs, it does demonstrate that it is possible to recover
two independent streams of information from the same magnetic track.
- Franc Zabkar
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