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Distinguishing between a degaussed Hard disk drive and a crashed hard disk & degausser common both both disks & tapes

Posted on 2010-09-24
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Last Modified: 2013-11-14

Curious, does vendors like HP & Sun have the means to distinguished
if faulty hard disk drives returned to them have been degaussed ?

A degaussed hard disk can't be used anymore while a disk drive that's
crashed (ie it's platter surface damaged?) are both physically damaged,
so in both cases, the hard disks can't be reformatted & reused anymore.

How then would the vendors be able to tell if the disks returned to them
have been degaussed & not of other physical damage?


Also, I've seen colleagues placing a hard disk into a degausser machine.
If we place a piece of tape into the degausser, would it also degauss
the tape securely such that it's data is beyond retrieval anymore?
Or we need different degaussers for disks & tapes ?
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Question by:sunhux
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by:Dave Baldwin
Dave Baldwin earned 180 total points
ID: 33755941
You should probably look up the spec for disks and tapes.  I think the tapes don't require as much power so it should work for them.

As for telling the difference between crashed and degaussed, the answer would be yes... except that it's manual labor in disassembling the disk.  That would probably cost more than a new disk so I don't know why they would do it.  If a drive crashed on the inner tracks, they might be able to read the first tracks and tell it was crashed.
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by:Dr. Klahn
Dr. Klahn earned 100 total points
ID: 33759068
Degaussers go back to the 1950s and were originally used for 9 channel magtapes with magnetically "soft" ferric oxide coating.  While a commercial degausser will (probably) make a drive largely unusable, I personally would not trust one to completely erase a disk drive; the coercivity of the plating on drive platters is much higher than amorphous ferric oxide.

No matter what data pattern is written to a drive, there are still magnetic transitions on the platters.  If the drive heads sense no flux transitions, then the drive has been degaussed.

Platter state and re-usability is determined at a depot repair facility when a drive assembly, minus controller PCB, is connected to a diagnostic station.
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by:Dave Baldwin
Dave Baldwin earned 180 total points
ID: 33759122
@DrKlahn, there are special high-powered degaussers made for erasing hard drives to government standards.  Don't get your keys or tools anywhere near them.  If you're interested, Google for "hard drive degausser".
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Author Comment

by:sunhux
ID: 33764417

I ask this question because I outsource degaussing of hard disks (Proliant & Dell servers
mainly) to another group who claims that they have degaussers for safe-erasure of
hard disks that conform to government standards.

> think the tapes don't require as much power so it should work for them.
Now, we just got a large bulk of tapes (LTO3/4 & DDS cartridges) & I'm contemplating
if that same group can do the degaussing of the tapes using the same degaussers
they've been using to degauss hard disks.   Can I safely assume if their degausser
could safely degauss hard disks, then the very same degausser could safely
degauss tapes as well?
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bmsjeff earned 150 total points
ID: 33766726
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by:andyalder
andyalder earned 70 total points
ID: 33769190
>Curious, does vendors like HP & Sun have the means to distinguished
if faulty hard disk drives returned to them have been degaussed ?

I think the disk head will be burnt out, whether they would test for that or just throw them away I'm not certain. You're not intending to degause them and then return them as faulty under warranty are you?
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Author Closing Comment

by:sunhux
ID: 33799598

Excellent
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