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

Mon Jan 30 09:19:08 EST 2012

On Fri, Jan 27, 2012 at 6:06 PM, Michael H. Warfield <mhw at wittsend.com>wrote:

> 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
>
> So if the drives were degaussed, they wouldn't even have shown up as
"Unformatted Disc" when plugged into a computer.  I didn't do the next
step, and attempt to format the drives.  I just sent them back to the
shipper.  They were the ones who said they had put the data on the discs.
Thanks for the very detailed explanation.

Wolf

> > 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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> --
> 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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