{
  "slug": "sector-disk-code",
  "term": "Sector-disk code",
  "aliases": [
    "SD code",
    "sector-disk erasure code"
  ],
  "definition": "A sector-disk code tolerates specified whole-column erasures plus arbitrary additional symbol erasures within an encoded array.",
  "note": "For an r-row, n-column stripe with m parity columns and s extra parity symbols, the SD guarantee covers any m columns plus up to s other erased symbols at arbitrary positions in that stripe. The redundancy is mr+s symbols, not m+s entire columns. [pmds14]\n\nPartial-MDS codes additionally cover any m erasures in each row plus s additional erasures, without requiring row losses to align in the same columns. [pmds14]\n\nThe 2014 construction addresses s=2 with stated field-size conditions; a family name does not certify arbitrary parameters or a particular encoder. [pmds14]",
  "related": [
    "stair-code",
    "erasure-coding",
    "reed-solomon-code",
    "latent-sector-error",
    "maximally-recoverable-code"
  ],
  "citations": [
    {
      "id": "pmds14",
      "title": "Blaum et al. Partial MDS (PMDS) and Sector-Disk (SD) Codes that Tolerate the Erasure of Two Random Sectors. ISIT 2014, Definition 1.1.",
      "url": "https://yaakobi.net.technion.ac.il/files/2015/04/34_PMDS_ISIT14.pdf",
      "accessed": "2026-10-24"
    }
  ],
  "status": "research",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-24",
  "provenance": [
    "The cited construction uses known erasure locations; its title's random sectors does not establish a failure probability model. [pmds14]"
  ]
}