{
  "slug": "patrol-read",
  "term": "Patrol read",
  "aliases": [
    "RAID patrol read"
  ],
  "definition": "Patrol read is a controller-managed background scan of eligible physical drives for media read errors.",
  "note": "Eligibility may include array members and hot spares while excluding unconfigured drives. Recovery depends on the error and array configuration, and concurrent maintenance can prevent a scan. This does not promise verification of every attached device. [perc11-patrol]\n\nSSD participation depends on the implementation. A management interface can accept a start request that later fails because no virtual disk exists, so request acceptance alone does not establish that scanning began. [idrac10]\n\nOverlapping consistency checking can interrupt patrol read; automatic restart depends on firmware. Retain completion, interruption and repair evidence, not only a schedule. Patrol read is distinct from comparing mirrored data or parity. [intel-patrol] [perc-consistency]",
  "status": "shipping",
  "advantages": [],
  "limitations": [
    {
      "text": "Media readability does not establish application-content correctness.",
      "citationIds": [
        "hesela-scrub"
      ]
    }
  ],
  "related": [
    "raid-consistency-check",
    "data-scrubbing",
    "latent-sector-error",
    "raid-rebuild"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "perc11-patrol",
      "title": "Dell PERC 11 User's Guide: Patrol Read, eligibility and concurrent operations",
      "url": "https://www.dell.com/support/manuals/en-ie/perc-h750-sas/perc11_ug/patrol-read?guid=guid-a088d58d-5552-4385-9aa0-6e6117350500&lang=en-us",
      "accessed": "2026-10-25"
    },
    {
      "id": "idrac10",
      "title": "Dell iDRAC10 1.20.xx: controller properties, patrol eligibility and job-start limitations",
      "url": "https://www.dell.com/support/manuals/en-us/poweredge-r670/idrac10_1.20.xx_ug/configuring-controller-properties?guid=guid-a02c24bf-0f11-4eac-a8a6-f6e5da9103c2&lang=en-us",
      "accessed": "2026-10-25"
    },
    {
      "id": "intel-patrol",
      "title": "Intel article 000023659: RS25/RMS25 patrol-read interruption and firmware-dependent restart",
      "url": "https://www.intel.com/content/www/us/en/support/articles/000023659/server-products/raid-products.html",
      "accessed": "2026-10-25"
    },
    {
      "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": "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": [
    "Dell PERC 11 supplies the configured-member, hot-spare and maintenance restrictions; other controllers need their own eligibility check. [perc11-patrol]",
    "Dell iDRAC10 1.20.xx lists SSDs as excluded and describes a job-start failure without a virtual disk; the SSD rule must not be generalized. [idrac10]",
    "Intel article 000023659 describes firmware-dependent interruption and restart on the RS25/RMS25 families. [intel-patrol]",
    "Documentation review, not a controller experiment, optimal-interval calculation or measured reduction in data loss."
  ],
  "updated": "2026-10-25"
}