{
  "slug": "mirror-set",
  "term": "Mirror set",
  "aliases": [
    "Mirror group",
    "Mirrored set"
  ],
  "definition": "A mirror set is a group of storage members configured to maintain copies of the same logical data.",
  "note": "OpenZFS permits mirrors with two or more members: an N-member mirror can retain its data after N-1 complete member failures when the remaining copy is current and readable. Multiple top-level data mirrors hold different portions of a pool; they are not copies of the entire pool. [zconcepts23] A set is a redundancy group, whereas a failure domain identifies a shared cause of unavailability. The fixed-pair example counts failure sets that remove every copy from at least one pair; it does not estimate real failure rates. [hesela-mirror-topology]",
  "status": "shipping",
  "advantages": [],
  "limitations": [
    {
      "text": "A configured but unsynchronized replacement does not yet provide a complete current copy.",
      "citationIds": [
        "zattach23"
      ]
    }
  ],
  "related": [
    "mirroring",
    "raid-10",
    "failure-domain",
    "resilver"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "zconcepts23",
      "title": "OpenZFS 2.3: zpoolconcepts(7), mirror virtual devices",
      "url": "https://openzfs.github.io/openzfs-docs/man/v2.3/7/zpoolconcepts.7.html",
      "accessed": "2026-10-15"
    },
    {
      "id": "zattach23",
      "title": "OpenZFS 2.3: zpool-attach(8), redundancy after resilver",
      "url": "https://openzfs.github.io/openzfs-docs/man/v2.3/8/zpool-attach.8.html",
      "accessed": "2026-10-15"
    },
    {
      "id": "hesela-mirror-topology",
      "title": "Hesela: RAID 10 mirror topology and exact failure-set counts",
      "url": "https://hesela.com/analyses/raid-rebuild-ure-math-and-resilver/#mirror-topology-heading",
      "accessed": "2026-10-15"
    }
  ],
  "updated": "2026-10-15"
}