{
  "slug": "codeword",
  "term": "Codeword (storage ECC)",
  "aliases": [
    "ECC codeword"
  ],
  "definition": "A storage ECC codeword is an encoded unit representing a data chunk together with error-correction redundancy.",
  "note": "A NAND page can hold multiple codewords. Codeword length and protected payload length are different quantities when redundancy is included; report which one a size or error-rate denominator uses. A codeword is not automatically a sector, NAND page or erase block. [cai2017]",
  "limitations": [
    {
      "text": "A count of failed codewords does not count every erroneous bit in those words.",
      "citationIds": [
        "cai2017"
      ]
    }
  ],
  "related": [
    "error-correcting-code",
    "ldpc",
    "reed-solomon-code",
    "nand-flash",
    "bit-error-rate"
  ],
  "citations": [
    {
      "id": "cai2017",
      "title": "Cai et al. Error Characterization, Mitigation, and Recovery in Flash Memory Based Solid-State Drives (2017), sections II.C and VI.C.",
      "url": "https://research.ece.cmu.edu/safari/pubs/1706.08642.pdf",
      "accessed": "2026-10-12"
    },
    {
      "id": "hesela-ldpc",
      "title": "Hesela: LDPC in NAND, the read cost of confidence.",
      "url": "https://hesela.com/analyses/ldpc-soft-decoding-read-cost/",
      "accessed": "2026-10-12"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-12"
}