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- How can Heat-assisted disks be bulk erased?
October 1, 2013, 6:17 pm
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at home by using a (somewhat dangerous) permanent magnet.
Will it be possible to bulk-erase disks at home when
heat-assisted magnetic recording (HAMR)is used on disks?
Perhaps the Curie temperature will be low enough and
nothing very poisonous will be generated by
bulk heating the disk media when HAMR is used.
Currently things have to be heated high enough so
that there isn't a good way to heat disks inside
a typical apartment. However the magnets from some
old, but post 2000 drives are strong enough to demagnetize
the actual disks in circa 2012 drives.
(Scratching the disk media doesn't do a good job
or erasing the data. Comparing the data rate
of about 150 MB/second with the size of the disk
gives about 50 bytes/linear mil. Thus, even if you
make the scratches deep enough to get rid of the recorded
signal, it is highly likely that areas 100's of
bytes long by 10's to 100's of tracks wide are undamaged.)
(Using a sander with 800 grid abrasive might
do the job circa 2012 and perhaps with HAMR disks,
but this may not be practical in a small apartment.)
Re: How can Heat-assisted disks be bulk erased?
From what little I've read about HAMR, it uses a laser to heat up the
spot for the recorded bit. The idea is probably to make the dipoles
align quicker and more perpendicular to differentiate them from one
another. Dipole toggling will still work via a degaussing field.
A unidirectional field magnet does not seem it would be as effective for
erasing magnetic media; that is, a permanent magnet, even if moved
around by hand, doesn't produce a good degaussing field. You want the
flip the dipoles back and forth and in a random order while removing the
degaussing field. A permanent magnet, if strong enough, would move the
dipoles just one so the all aligned in the same direction. Of course,
maybe you're not talking about permanent magnets you find at home or
even those super strong ones at the hobby shop. Maybe you're talking
about one of these:
At home, for catastrophic data destruction at home, just open the case
to dismantle and remove the platters, put on protective eyewear, and use
a sledge on the platters. If that isn't sufficient, use a hand grinder
on the platters.
Re: How can Heat-assisted disks be bulk erased?
I didn't do the calculation closely enough. Seagate circa 2012 has
240,000 tracks per inch, so 240 tracks per mill, so a 1 mil
square that didn't get destroyed would be about 50 bytes by
240 tracks. (Up to 340,000 by 2013)
I saw some of those things, but they were too expensive for me.
This is something with a varying magnetic field. I don't know
if it is line frequency or a higher frequency.
This thing seems like a permanent magnet:
Datastroyer 102-DG Disk Erasing Wand Degausser
Whitaker Brothers | SKU: WHI102
"Basic Specs of the 102 DG Degausser
Destruction type: magnetic degaussing (all magnetic media)
Must remove platter from hard drive prior to degaussing for NSA
Evaluated Media Storage Destruction
Typical peak flux: 8,000+ gauss
Dimensions: 7" L x 1 1/2" W x 1/4" D
Weight: 2 lbs."
Elsewhere on the page it says:
"Magnetic Flux Density 12,000 (maximum flux)"
"DG is a handheld data erasing device which produces an intense,
continuous 4-pole magnetic field"
About US$750 from the manufacturer
It seems link putting the platter between two attaching magnets
would be more effective. (I don't know if this is true, but it is
the method that I use.)
US Government price is US$2850. I don't know what the civilian price
The manufacturers web page says it replaces an older model that
doesn't work with recent drives. However, while the older model
was supposed to work with disk platters the newer model only lists
For about US$25000, there seem to be units to erase and entire disk
drive without taking it apart. These typically have a hand crank to
move the drive through the magnetic field.
I didn't see anything for disk platters that would allow for
controlled movement of disk platters though a permanent or AC
I don't know about any of these products and am just reporting stuff
found via Google.
I used to use a sander on the platters, but I no longer have a place
to sand stuff and don't want to be near the dust anyhow, even with a
dust mask that I can get at Home Depot.
I also found that I can boil things or heat them red hot, but
I can't get a controlled temperature those points.
The platters melt on my gas stove, giving off fumes that I don't
like and messing up the stove, so that is a no go.
I could try putting platters in an oven at up to 550F (280C)
I'd be afraid to put platters in the self cleaning cycle of
an oven. I couldn't find a clear curie point for all of the
likely materials. Numbers from 80C to 1200C seem to be in the
By the way, here is another HAMR paper:
"Heat Assisted Magnetic Recording"
By Mark H. Kryder, Edward C. Gage, Terry W. McDaniel, William A.
Robert E. Rottmayer, Ganping Ju, Yiao-Tee Hsia, and M. Fatih Erden
"Proceedings of the IEEE", Volume 96, Number 11, November 2008
Seems good, but it is 5 years old.
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