I doubt they place any of the drive parameters on the magnetic media
itself.  Should be located in a flash or eeprom.  The plates do,
however, contain one or more servo tracks.  The most recent
high-capacity drives actually contain one servo track for each regular
track, and the head has two sensors, one that sits on the servo track
and another that reads the data track.

The servo track helps improve seek time (the head can slam around a bit
faster) and provides the feedback necessary to stay ona track once the
head gets there - the voice coil is then in a closed loop mode.

It would take a lot of external magnetic field to change the information
on the platter.  But if you blew more than a few servo tracks then the
drive would probably run out of 'extra' replacement storage space and
start reporting errors if it didn't cease to function alltogether.

As a note, the click of death experienced by many Zip disk users was
traced to servo tracks being inadvertently overwritten on the media.
The head would continue to look for the servo tracks...
click...click...click...

-Adam

Liam O'Hagan wrote:

>Don't hard drives have some sort of onboard controller, which may be
>scrambled by the scanner?
>
>
>
>>-----Original Message-----
>>From: Jake Anderson [SMTP:grooveee@OPTUSHOME.COM.AU]
>>Sent: Monday, February 09, 2004 1:45 PM
>>To:   PICLIST@MITVMA.MIT.EDU
>>Subject:      Re: [EE:] What are acceptable Hard Disk shipping packaging
>>standards?
>>
>>the magnetic scanner really shouldn't do any harm. it might hash the drive
>>contents but the only real danger would be induced currents in the drive
>>PCB
>>and they really should be minimal.
>>
>>
>>
>
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>
>
>
>
>

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