[ale] OT could a metal detector in shipping process do this?

[Michael H. Warfield]

On Fri, 2012-01-27 at 16:38 -0500, Wolf Halton wrote:
> I am not going down to bit-level analysis, but plug them in and both the
> gnome disk utility and windows' similar app tell me that the disks are
> unformatted.

Fine.  They're unformatted.  Format the buggers.

Seriously...  They COULD NOT have been damaged by metal detectors or any
other magnetic influence (other than being hooked up to a computer) and
even operate.

Warning...  Extreme low level details to follow...

Old OLD drives use to have stepper motors and the tracking was very
course.  You could wipe out every bit on every platter and recover that
drive because the tracking was determined by the increments of the
motor.  Slightly more modern variations use actuators with various
sensors.  But we're talking in the few Meg range here.

Later drives dedicated an entire platter surface as a "servo surface"
and the heads where driven by magnetic solenoid actuators that took quad
phase signaling from the servo platter to control where the trackers
where.  THIS is the era of Steve Gibson and SpinRite.  Drives would age
and the actuator arms would flex and change in time and tracks would get
out of alignment and start showing errors because they now longer
aligned with the server platter.  SpinRite could correct this by
rewriting the tracks and they would once again be in alignment (they're
aligned to where the are written last).  If a track on a data platter
was lost, you lost data.  If a track on the servo platter was lost, you
lost that entire cylinder and several cylinders near-by.  If a magnetic
field could destroy a data track, it could destroy the servo platter and
the drive it toast.  There was a "low level format" for those drives but
you STILL needed the servo platter.  There were in the hundreds of Megs
to a few Gig for some very expensive models.

That's ancient technology.  Modern drives (last 15 years or so) embed
the servo data in the gaps between the sectors.  There is no "servo
platter" (and 90% of the value of SpinRite is now BullShit) and the
drive actuator system aligns itself through a feedback mechanism each
time a gap passes underneath it.  You may rewrite sectors but the
sectors are aligned not to a servo platter but to the quad phase signals
in the gaps before and after the sector.  So they CAN NOT DRIFT like the
old drives.  But, again, if something destroys that signaling, you can
not format it, the drive is simply toast and will throw errors and
simply fail to initialize.

In modern day lingo, formatting is purely high level.  If the drive
works at all without giving errors, then the tracking and sync patterns
and true "low level" formatting are present and invisible to you and
nothing in shipping can damage the high level formatting without
destroying the low level formatting without breaking the box open and
hooking it up to something.

It just wasn't formatted.  No big deal.  Could you format it?  Could you
partition it?

Mike

> On Fri, Jan 27, 2012 at 3:32 PM, Michael Trausch <mike at trausch.us> wrote:
> 
> > By "entirely unformatted" I presume the disk is full of zeroes? If that is
> > the case, the shipper most likely made a mistake...
> >
> > --
> > Sent from my CyanogenMod mobile device.
> > Please excuse any typos.
> > On Jan 27, 2012 3:01 PM, "Wolf Halton" <wolf.halton at gmail.com> wrote:
> >
> >> I have 4 hard drives sent to me. One of the 4 is entirely unformatted
> >> while the other three are formatted  (and full of data).
> >> Is there any way that a metal detector or some-such DHS TSA device could
> >> entirely clear 1 of 4 discs??
> >>
> >> The sender said there was data on all the disks when they were packaged
> >> up.
> >>
> >> --
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> >>
> >>
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-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
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