{
  "status": "shipping",
  "advantages": [],
  "limitations": [
    {
      "text": "Automatic activation depends on the platform's fault-management services and configuration; merely listing a spare does not prove replacement has started.",
      "citationIds": [
        "zpoolmonitor"
      ]
    }
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-13",
  "slug": "hot-spare",
  "term": "Hot spare",
  "aliases": [
    "Standby spare"
  ],
  "definition": "A hot spare is a standby device or reserved distributed spare capacity available to take over a failed member's role in a redundant array or pool.",
  "note": "An unused spare is not an already synchronized extra member or an independent backup: replacement still requires reconstruction [zreplace]. In ZFS, spare activation and replacement state are distinct from completed resilvering [zconcepts]. A spare shortens the wait for replacement capacity; it does not add a parity level. OpenZFS documents ZED consuming pool events to automate replacement; monitoring and reconstruction completion still need separate checks [zpoolmonitor].",
  "related": [
    "raid-rebuild",
    "degraded-array",
    "resilver",
    "raid",
    "mirroring",
    "distributed-spare"
  ],
  "citations": [
    {
      "id": "zconcepts",
      "title": "OpenZFS 2.3: zpoolconcepts(7), device failure and hot spares",
      "url": "https://openzfs.github.io/openzfs-docs/man/v2.3/7/zpoolconcepts.7.html",
      "accessed": "2026-10-13"
    },
    {
      "id": "zreplace",
      "title": "OpenZFS 2.3: zpool-replace(8), replacement and sequential reconstruction",
      "url": "https://openzfs.github.io/openzfs-docs/man/v2.3/8/zpool-replace.8.html",
      "accessed": "2026-10-13"
    },
    {
      "id": "hesela-rebuild",
      "title": "Hesela: RAID rebuild read-error models and resilver boundaries",
      "url": "https://hesela.com/analyses/raid-rebuild-ure-math-and-resilver/",
      "accessed": "2026-10-13"
    },
    {
      "id": "zpoolmonitor",
      "title": "OpenZFS 2.3: zpool(8), monitoring and event-driven spare replacement",
      "url": "https://openzfs.github.io/openzfs-docs/man/v2.3/8/zpool.8.html",
      "accessed": "2026-10-13"
    }
  ]
}