HDD (HDD)

HDD stands for hard disk drive, a magnetic data storage device that records bits as magnetic polarities on spinning rigid platters read and written by a moving actuator arm with a magnetic head. HDDs were the dominant computer storage technology from 1990 to roughly 2018, and the installed base in Indian offices, government, and data centres is still in the tens of millions of units.

Composition and value: A standard 3.5-inch desktop HDD weighs 500-700 grams. Roughly 30-40% by mass is high-grade die-cast aluminium (the chassis), 30-35% is steel (the cover, screws, and motor laminations), 10-15% is the polished aluminium-substrate or glass-substrate platters coated with a thin cobalt-platinum-chromium magnetic film, 5-8% is the actuator arm assembly, and 3-5% is the controller PCB. The single highest-value component is the voice-coil motor: a powerful neodymium-iron-boron (NdFeB) rare-earth magnet weighing 12-25 grams per drive. Aggregated across 10,000 drives, this is 150-250 kg of high-grade rare-earth magnet — a meaningful secondary supply.

Data destruction comes first: Before any recycling step, the drive must undergo certified data destruction. The two NIST-accepted methods are degaussing (magnetic field strength of 15,000-20,000 gauss applied to scramble all data) and physical destruction (shredding to particles 6 mm or smaller, or controlled crushing of the platters). Indian corporate and government clients increasingly require an NIST SP 800-88 Rev. 1 compliance certificate, an audit trail with each drive serial number, and witnessed destruction. GDPR-bound European clients impose even stricter chain-of-custody requirements.

Trade-offs: Degaussing preserves the aluminium platter but destroys any resale value as a working drive; physical shredding destroys both the data and the rare-earth magnet recovery potential. Best practice is to dismantle the drive in a clean room, extract the intact neodymium magnet for resale or rare-earth refining, then degauss or shred the platter separately. This adds 2-3 minutes of labour per drive but raises recovery value by Rs 20-40 per unit.