{
  "slug": "raid-consistency-check",
  "term": "RAID consistency check",
  "aliases": [
    "RAID redundancy check"
  ],
  "definition": "A RAID consistency check tests whether redundant representations agree, such as mirrored blocks or parity and their associated data.",
  "note": "A controller consistency check can verify and correct mirror or parity data on fault-tolerant virtual disks. This is a redundancy-level operation, distinct from patrol read and from filesystem or application validation. [perc-consistency] [hesela-scrub]\n\nThe mdadm 4.2 manual distinguishes readable mismatches from read errors. MD check records the former without reconciling them, but normal read-error recovery can still write reconstructed data. MD repair can rewrite parity or mirror copies; the command name check is not a write-free guarantee. [md4-scrub]\n\nAgreement alone does not identify the intended payload. Two matching copies can contain the same wrong application output. A single-error model shows that unvalidated maintenance reads can propagate bad data into parity. This does not establish that every controller behaves that way. [parity-model] This is an integrity-boundary inference, not a measured fault rate. Retain coverage, completion, mismatches and repair actions separately. [hesela-scrub]",
  "status": "shipping",
  "advantages": [],
  "limitations": [
    {
      "text": "Repair policy and write behavior depend on the implementation and selected operation.",
      "citationIds": [
        "perc-consistency",
        "md4-scrub"
      ]
    }
  ],
  "related": [
    "patrol-read",
    "data-scrubbing",
    "md-mismatch-count",
    "parity-inconsistency",
    "parity-pollution",
    "checksum",
    "raid-rebuild"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "perc-consistency",
      "title": "Dell KB 000139796: PERC Check Consistency, mirror and parity correction",
      "url": "https://www.dell.com/support/kbdoc/en-us/000139796/perc-how-to-perform-a-check-consistency-using-openmanage-server-administrator",
      "accessed": "2026-10-25"
    },
    {
      "id": "md4-scrub",
      "title": "mdadm 4.2 md(4): Scrubbing and mismatches, read-error handling versus readable mismatches",
      "url": "https://manpages.debian.org/bookworm/mdadm/md.4.en.html",
      "accessed": "2026-10-25"
    },
    {
      "id": "parity-model",
      "title": "Krioukov et al. Parity Lost and Parity Regained. FAST 2008, sections 3-4.",
      "url": "https://www.usenix.org/legacy/event/fast08/tech/full_papers/krioukov/krioukov_html/main.html",
      "accessed": "2026-10-25"
    },
    {
      "id": "hesela-scrub",
      "title": "Hesela: patrol read, RAID consistency and verification boundaries",
      "url": "https://hesela.com/analyses/scrubbing-detection-not-durability/#controller-checks",
      "accessed": "2026-10-25"
    }
  ],
  "provenance": [
    "The controller example is Dell PERC; Linux MD behavior is separately qualified using the mdadm 4.2 manual. [perc-consistency] [md4-scrub]",
    "No maintenance command was executed and no optimal checking interval is claimed."
  ],
  "updated": "2026-10-25"
}