Which outcome should a server administrator expect after passing a stack of 3.5-inch magnetic HDDs through an NSA-listed degausser during the decommissioning process?
All user sectors are overwritten with zeros, but servo tracks remain, so the drive can be low-level formatted and reused.
Only file-system tables are removed, meaning most user files could still be recovered with forensic tools.
The magnetic coating is heated past its Curie point, warping the platters and creating an indoor safety hazard.
The platters and factory servo data are demagnetized, making the drive permanently unusable and the data unrecoverable.
A degausser generates a very strong magnetic field that scrambles every magnetic domain on the platters. Modern hard disk drives keep their factory-written servo tracks-used to position the read/write heads-on those same platters. When the servo information is erased along with user data, the firmware can no longer locate tracks, the drive will not initialize, and it is permanently unusable. Overwriting with zeros keeps servo data intact so the drive can be repartitioned; deleting file-system metadata removes only pointers, leaving the bulk of data recoverable; and vaporizing magnetic coatings is a characteristic of thermal or physical destruction methods, not degaussing. Therefore, the only correct expectation is that degaussing both destroys the data and renders the drive inoperable.