{
  "status": "research",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-19",
  "slug": "interleaved-parity",
  "term": "Interleaved parity",
  "aliases": [
    "Interleaved parity check",
    "IPC"
  ],
  "definition": "Interleaved parity assigns separated data positions to independent parity groups so that a short contiguous loss can be distributed across those groups.",
  "note": "The XOR construction reviewed in FAST 2010 groups every m-th data sector with its parity sector [schroeder].\n\nIn Hesela's 16+2 byte example, even and odd positions form two groups of nine. All 17 adjacent pairs are recoverable, but only 81 of all 153 two-position erasure sets are. Losing positions 0 and 2 leaves two unknowns in one group. These are exact constructed-pattern counts, not fault probabilities [hesela-layout].\n\nKnown erasure locations and correct, version-consistent survivors are assumptions. Two parity bytes do not by themselves establish an MDS any-two-loss guarantee [hesela-layout].",
  "related": [
    "intra-disk-redundancy",
    "maximum-distance-separable-code",
    "symbol-erasure",
    "latent-sector-error"
  ],
  "citations": [
    {
      "id": "schroeder",
      "title": "Schroeder, Damouras and Gill. Understanding latent sector errors and how to protect against them. FAST 2010, section 4.",
      "url": "https://www.usenix.org/legacy/events/fast10/tech/full_papers/schroeder.pdf",
      "accessed": "2026-10-19"
    },
    {
      "id": "hesela-layout",
      "title": "Hesela: Interleaved XOR parity, complete erasure-pair enumeration",
      "url": "https://hesela.com/analyses/scrubbing-detection-not-durability/#intradisk-parity",
      "accessed": "2026-10-19"
    }
  ]
}