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Greg Barniskis
nalists at scls.lib.wi.us
Fri Jan 21 06:51:07 PST 2005
Ian Moore wrote:
> Tape de-gaussers usually aren't much good - they were mostly made for erasing
> open reel tape that used ferric oxide particles.
> Backup tapes normally use metal particle tapes that need a much stronger
> magnetic field to effectively erase them.
More powerful degaussers are available, like the one found at
http://www.datalinksales.com/degaussers/hd1.htm
Not cheap (about $5k if memory serves), but seems to do the job on
both HDs and modern tapes (what the company calls "coercive media").
We have not found it necessary to remove the HD platters from their
enclosures, although I imagine that might yield more thorough
results. We just make two passes for better peace of mind.
I also imagine that data on degaussed platters might still be
available to the kinds of inspection techniques used on platters
overwritten with random data, but our acceptable cost/reward balance
tops off somewhere above preventing casual inspection and below
stopping the NSA. One way that degaussing is more effective than
random data writing is that the disk's servo tracks are also
destroyed, meaning you'd probably need to return the device to the
OEM for factory reconditioning before anyone could usefully attach
it to another computer. I hope it's true, as that was our primary
justification for the cost of the degausser.
--
Greg Barniskis, Computer Systems Integrator
South Central Library System (SCLS)
Library Interchange Network (LINK)
<gregb at scls.lib.wi.us>, (608) 266-6348
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