{
  "slug": "head-disk-interface",
  "term": "Head-disk interface (HDI)",
  "aliases": [
    "HDI",
    "head disk interface"
  ],
  "definition": "The head-disk interface is the interacting region between an HDD's head-carrying slider and rotating disk surface.",
  "note": "The interface involves gas-film support, local clearance and surface interactions, not the SATA or SAS host connection. Ma et al. distinguish passive flight, touchdown transition and stronger modulation using specialized head-media spacing and touchdown-sensor signals [touchdown]. A controlled contact experiment is not a count of catastrophic failures in an operating fleet [analysis].",
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "related": [
    "hdd",
    "flying-height",
    "thermal-flying-height-control",
    "rotational-vibration",
    "head-slap",
    "touchdown-sensor"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "touchdown",
      "title": "Ma et al.: Head disk interface characterization, CML report 15013, introduction and experiment",
      "url": "https://cml.berkeley.edu/wp-content/uploads/blue-reports/15013.pdf",
      "accessed": "2026-10-15"
    },
    {
      "id": "analysis",
      "title": "Hesela: HDD mechanical faults, evidence and diagnostic limits",
      "url": "https://hesela.com/analyses/hdd-mechanical-failure-points/",
      "accessed": "2026-10-15"
    }
  ],
  "updated": "2026-10-15"
}