[wellylug] Magnetic tape question

[Robin Hinde]

On Wed, 17 Dec 2003 12:22, Peter Jones wrote:
> Slightly off topic, but as this is a place where knowlegeable people
> visit...
>
> I have a number of DLT IV tapes that have been used in an older DLT tape
> drive, and now cannot be used in a DLT I.
> Looking at the Benchmark web site (Benchmark tape drives, not the hardware
> store) there is an entry in the FAQ that indicates
> the tapes need to be bulk erased. The eraser needs to be a Big Healthy one,
> capable of generating a magnetic field of about 4000 or more Oersteds
> http://www.4benchmark.com/support/faqDetail.cfm?faqID=55
>
> "While most older magnetic media technologies have coercivity ratings of
> well below 750 Oersteds, and many of today's technologies are rated up to
> 1500 Oersteds, DLTtape(tm)IV media is rated at 1850 Oersteds. The
> degaussing equipment being used must have an Oersted rating at least equal
> to, and preferably two to three times greater than, the coercivity rating
> of the media being degaussed."
>
> Anyone know of a site with equipment that would suit?

I'd say you are SOL:

"US Government guidelines class tapes of 350 Oe coercivity or less as 
low-energy or Class I tapes and tapes of 350-750 Oe coercivity as high-energy 
or Class II tapes. Degaussers are available for both types of tapes. Tapes of 
over 750 Oe coercivity are referred to as Class III, with no known degaussers 
capable of fully erasing them being known [19], since even the most powerful 
commercial AC degausser cannot generate the recommended 7,500 Oe needed for 
full erasure of a typical DAT tape currently used for data backups."

The above from Peter Gutman's article at

http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

Of course, the NSA might have something.

<OT>

Peter Gutman's article is a *really* interesting read, BTW. Most people here 
will be aware that data can be recovered from magnetic media, but probably 
not aware that recovery of data is possible from RAM also.

</OT>

cheers

  -=rjh=-