Re: [MLUG] favorite shredder utility

[norgardp <EMAIL:PROTECTED>]

> > > Why is that?  After all bits have been flipped to zero, where is the
> > > information stored about their previous states?
> 
> Seriously though, how is the information about previous states of bits
> stored on the drive?  It would seem to imply that the drive has a much
> greater capacity than we usually think -- it can hold the current
> information and also past information.  But how?
> 
> Mike

Actually you make an interesting point. The drive itself probably has much 
more capacity than the manufacturer states. They must take into account 
the effects of numerous mechanical nuances in their read/write heads. If 
you've ever cannibalized a drive, you'll find that the heads are mounted 
on razor-thin arms. Being that they are this thin, it seems likely that at 
some point vibrations must come into play. 

Additionally, the placement of the heads over the proper track will 
invariably result in overshoot. This means that the region that gets 
written to is not necessarily the *same* region that gets read or even 
re-written to.

Statistically, you should write random garbage up to the CIA standard of 
something like 100 times. That's more than likely enough to 'touch' the 
entire surface of you drive.

If you want more info on the subject search for Spinrite (fat based). The 
site has links to drive recovery and destruction sites. Interesting 
reading. (me thinks it's at grc.com [as typed], under spinrite).

hth...cheers

Peter Norgard
University of Missouri - Columbia

EMAIL:PROTECTED

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