What is hard drive degaussing and how does it work?

19 March 2020 by Tilly Holland

There are some reliable and inexpensive ways to sanitise data securely, and above all, irrevocably. There are two possible methods that you can use for sanitising devices that you don’t plan on using again – demagnetisation using degaussing or mechanical destruction via shredding.

Both solutions work well in the case of defective equipment and when the hardware necessary to access the data no longer exists. However, those responsible have to understand that using either a shredder or degausser results in the media becoming unusable.

What is a hard drive degausser?

Degaussing is a unique technique of the permanent deletion of data applicable to memory devices based on a magnetic media (hard disk, floppy disk, magnetic tapes on open reels or cassette). It can ensure the rapid sanitisation of information from media where it is not possible to apply to overwrite erasure software due to hardware failure.

How does degaussing work?

The physical principle underlying the degaussing relies on the polarisation of the Weiss domains. The data is stored on magnetic media, such as hard disks and tapes, whereby a magnetic field is applied to very small areas called magnetic domains, specifically Weiss domains. This process is based on the theory developed by French physicist Pierre Weiss. The magnetic field while in the writing phase of the information impresses a verse that orients the magnetisation of a certain number of Weiss domains. These verses of the magnetisation are associated with bit values 0 and 1.

By subjecting magnetic media to degaussing, the magnetisation arrangement of the Weiss domains that were generated when writing the data to the unit is no longer organised but forced into one direction, erasing the data.

The demagnetisation process employs the use of an adequately powered hardware tool called a degausser. In contrast to overwriting software programmes, the time taken to complete an erasure through degaussing can be standardised, no matter what type of media or its data capacity. Another difference from overwriting erasure software is that a device subjected to demagnetisation is no longer reusable.

What does degaussing do to a hard drive?

A magnetic field of such power not only offers the guarantee of successful elimination of data from newer hard disks but also to safeguard the investment of the future with the use of disks that have a high recording density and coercivity factor.

Not all degaussers can delete data from hard drives and tapes permanently. You must bear in mind that a magnet opposes some resistance to demagnetisation - magnetic coercivity. Coercivity is the intensity of the reversed magnetic field that must be applied to a material to cancel its magnetisation. For a degausser to be effective, it is necessary that it is able to generate a magnetic field of at least equal to 1.5 times the coercivity of the support that needs to be deleted.

What follows is that the higher the power of the degausser, the greater its effectiveness and the possibility to use it on future technology hard disks and other magnetic media. The degaussing procedure lasts only a few seconds; place the device in the compartment and push a button to initiate the demagnetisation. The media will not be reusable after this procedure.

What storage media can be degaussed?

A degausser can securely sanitise all magnetic storage devices.

  • 5 ¼, 3 ½ or 2 ½-inch hard disk drives
  • Digital magnetic tapes of all popular formats: LTO, DLT, etc.
  • 5 ¼ and 3 ½-inch floppy disks

Do you want to know more about degaussing? At Ontrack, we have a range of data sanitisation methods that will ensure the 100% destruction of your media. Get in contact with one of our data erasure specialists today.



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