{
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-25",
  "slug": "vdev",
  "term": "ZFS virtual device (vdev)",
  "aliases": [
    "vdev",
    "ZFS virtual device",
    "virtual device (ZFS)"
  ],
  "definition": "A ZFS virtual device (vdev) is a node in a pool's storage hierarchy representing a backing device or a supported device arrangement such as a mirror or RAIDZ group.",
  "note": "A leaf vdev is a backing endpoint; a top-level vdev sits directly below the pool's root. Normal pool allocations span top-level data vdevs, while mirror or parity redundancy operates within each group. Losing a required data-bearing top-level vdev beyond its redundancy can make the pool unavailable and cause data loss. [vdev-guide]\n\nA leaf can be a disk, partition or experimental file backing. An unused spare is replacement capacity, not extra current replicas. Cache devices hold read-cache copies; log devices hold separate intent-log blocks. The special and dedup classes hold authoritative allocated blocks, not disposable caches. Roles and redundancy must be checked separately; an individual member failure is not automatically whole-pool loss. [pool-man]",
  "related": [
    "zfs",
    "raidz",
    "zfs-separate-log",
    "mirroring",
    "failure-domain",
    "resilver"
  ],
  "citations": [
    {
      "id": "vdev-guide",
      "title": "OpenZFS: VDEVs, pool hierarchy and redundancy boundaries",
      "url": "https://openzfs.github.io/openzfs-docs/Basic%20Concepts/Pool%20Structure/VDEVs.html",
      "accessed": "2026-10-25"
    },
    {
      "id": "pool-man",
      "title": "OpenZFS 2.3: zpoolconcepts(7), device roles and failure states",
      "url": "https://openzfs.github.io/openzfs-docs/man/v2.3/7/zpoolconcepts.7.html",
      "accessed": "2026-10-25"
    }
  ],
  "provenance": [
    "Pool hierarchy uses the OpenZFS Basic Concepts terminology: root, top-level and leaf.",
    "Failure statements concern required data-bearing vdevs, not every cache, spare or log event; no availability probability is claimed."
  ]
}