{
  "slug": "optinand",
  "term": "OptiNAND",
  "aliases": [],
  "definition": "OptiNAND is a flash-assisted HDD architecture that integrates an embedded iNAND device with disk-controller hardware and firmware.",
  "note": "Flash holds drive metadata, including sector-level write accounting for targeted ATI refresh; it does not by itself determine whether recording uses CMR or SMR. [wd-brief]\n\nThis is not synonymous with a hybrid drive's user-data read cache. ArmorCache is a distinct supported-model feature for retaining buffered writes on emergency power loss, so OptiNAND flash can also contain user data. [wd-armor]",
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "related": [
    "hdd",
    "ati-refresh",
    "armorcache",
    "sshd"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "wd-brief",
      "title": "Western Digital. Reimagining HDDs with OptiNAND Technology, August 2022, printed pp. 1-4.",
      "url": "https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/collateral/tech-brief/tech-brief-reimagining-hdds-with-optinand-technology.pdf",
      "accessed": "2026-10-16"
    },
    {
      "id": "wd-armor",
      "title": "Western Digital. ArmorCache Write Cache Data Protection, mechanism and WCE/WCD scope, printed pp. 1-2.",
      "url": "https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/collateral/tech-brief/tech-brief-write-cache-data-safety.pdf",
      "accessed": "2026-10-16"
    },
    {
      "id": "hesela-boundary",
      "title": "Hesela. OptiNAND metadata is not the ArmorCache guarantee: model and system boundaries.",
      "url": "https://hesela.com/analyses/hdd-adjacent-track-interference-refresh/#optinand-armorcache",
      "accessed": "2026-10-16"
    }
  ],
  "updated": "2026-10-16",
  "provenance": [
    "OptiNAND is a Western Digital architecture. The cited technical briefs describe its design, not independent measurements of reliability or workload performance."
  ]
}