Degaussing for magnetic tape and legacy HDDs.
Magnetic media — LTO/DLT tape, optical media, legacy magnetic HDDs — is impractical to wipe in any reasonable time. Default destruction: degauss to obliterate magnetic alignment, followed by particle-size shred for high-classification loads.
Coercivity-matched degauss vs degauss-then-shred.
Degaussing applies a strong alternating magnetic field that randomises the magnetic alignment of the media's storage particles. Done correctly, the data on the media becomes unrecoverable.
Done correctly hinges on coercivity matching. Different generations of magnetic media have different coercivity (the magnetic-field strength needed to alter the alignment). LTO-9 has higher coercivity than LTO-2; modern perpendicular-recording HDDs have higher coercivity than older longitudinal-recording drives. The degausser must produce a field that exceeds the media's coercivity — under-strength degaussing leaves recoverable data.
For low-to-moderate classification: coercivity-matched degauss is sufficient. For high-classification: degauss-then-shred eliminates any residual risk plus addresses the physical media even if the magnetic state weren't fully randomised.
Tape and legacy magnetic media
- ♦ LTO-2 through LTO-9 — full cartridge degauss + shred.
- ♦ DLT tape — degauss + shred.
- ♦ 9-track magnetic tape (legacy mainframe) — degauss + shred.
- ♦ Optical media (CD, DVD, Blu-ray) — particle-size shred (no degauss, optical media isn't magnetic).
- ♦ Magnetic HDDs (older platters) — coercivity-matched degauss + shred for high-classification.
- ♦ Floppy disks (rare but sometimes encountered) — shred.
Maxicom Canada — frequently asked
Why can't we just wipe the tape instead of degaussing?
Tape capacity has grown faster than tape-write speed. Wiping a single LTO-9 cartridge by overwriting the full capacity would take roughly 10-15 hours per cartridge. For a backup-tape archive of thousands of cartridges, that's structurally impractical. Degauss takes seconds per cartridge.