{
  "slug": "hm-smr",
  "term": "Host-managed SMR (HM-SMR)",
  "aliases": [
    "host-aware SMR",
    "ZBC/ZAC host-managed"
  ],
  "definition": "An SMR HDD whose shingled bands are exposed to the host, which must write sequentially within zones.",
  "note": "Host-managed SMR exposes sequential-write-required zones: the host (or zoned filesystem) must write at the zone write pointer; out-of-order writes are rejected. Zone report/reset/finish commands come from SCSI ZBC or ATA ZAC with aligned semantics. Linux identifies host-managed disks as zoned block devices (`queue/zoned` = host-managed); SCSI type 0x14 or SATA signature 0xabcd distinguish them from ordinary disks. Unlike drive-managed SMR, there is no firmware mask for random block I/O—integration needs zone-aware software (e.g., zonefs, SMR-aware object layers). Vendors place top nearline capacities on HM-SMR because the host can keep writes sequential and performance predictable.",
  "status": "limited",
  "advantages": [
    {
      "text": "Host software can optimize placement for append-heavy workloads.",
      "citationIds": [
        "c1"
      ]
    }
  ],
  "limitations": [
    {
      "text": "Requires OS or application support for zoned block or zoned ATA commands.",
      "citationIds": [
        "c1"
      ]
    }
  ],
  "related": [
    "smr",
    "device-managed-smr",
    "zns"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "c1",
      "title": "Zoned block device",
      "url": "https://en.wikipedia.org/wiki/Zoned_block_device",
      "accessed": "2026-03-26"
    },
    {
      "id": "n2",
      "title": "Zoned Storage — Getting started with SMR hard disks",
      "url": "https://zonedstorage.io/docs/getting-started/smr-disk",
      "accessed": "2026-10-07"
    },
    {
      "id": "n3",
      "title": "Zoned Storage — Zoned storage devices overview (host-managed model)",
      "url": "https://zonedstorage.io/docs/introduction/zoned-storage",
      "accessed": "2026-10-07"
    },
    {
      "id": "n4",
      "title": "Zoned Storage — SMR introduction (ZBC/ZAC)",
      "url": "https://zonedstorage.io/docs/introduction/smr",
      "accessed": "2026-10-07"
    }
  ]
}