{
  "slug": "smr",
  "term": "Shingled magnetic recording (SMR)",
  "aliases": [
    "shingled recording"
  ],
  "definition": "An HDD recording method that overlaps tracks like roof shingles to raise areal density at the cost of rewrite behavior.",
  "note": "SMR raises areal density by overlapping successive write tracks like roof shingles: the write head is wider than the final readable track, so each pass trims the previous track to a narrow band the narrower reader can still sense. Tracks are grouped into zones with inter-zone gaps so the wide writer does not bleed across zone boundaries. Reads stay random-access; modifying a sector typically requires rewriting the affected shingled band. Hosts see one of three interface models—drive-managed (firmware hides constraints), host-aware (optional ZAC/ZBC optimization), or host-managed (mandatory sequential writes at the write pointer). INCITS T10 ZBC and T13 ZAC standardize the host-visible zone models; drive-managed has no separate command set because it presents as a conventional disk. SMR fits sequential/archive/object tiers; unmanaged random-write pools often prefer CMR.",
  "status": "shipping",
  "advantages": [
    {
      "text": "Higher areal density than conventional track layout on the same PMR platform.",
      "citationIds": [
        "c1"
      ]
    }
  ],
  "limitations": [
    {
      "text": "Random rewrite patterns may require host or drive-managed band relocation.",
      "citationIds": [
        "c1"
      ]
    }
  ],
  "related": [
    "cmr",
    "pmr",
    "hm-smr",
    "device-managed-smr",
    "nearline-hdd"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": {
    "date": "2013",
    "citationIds": [
      "c1"
    ]
  },
  "lastSeen": null,
  "citations": [
    {
      "id": "c1",
      "title": "Shingled magnetic recording",
      "url": "https://en.wikipedia.org/wiki/Shingled_magnetic_recording",
      "accessed": "2026-03-26"
    },
    {
      "id": "n2",
      "title": "Zoned Storage — Shingled Magnetic Recording hard disks",
      "url": "https://zonedstorage.io/docs/introduction/smr",
      "accessed": "2026-10-07"
    },
    {
      "id": "n3",
      "title": "Seagate — CMR and SMR hard drive list (workload guidance)",
      "url": "https://www.seagate.com/products/cmr-smr-list/",
      "accessed": "2026-10-07"
    },
    {
      "id": "n4",
      "title": "Western Digital — SMR HDD technology white paper",
      "url": "https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/collateral/white-paper/white-paper-shingled-magnetic-recording-hdd-technology.pdf",
      "accessed": "2026-10-07"
    }
  ]
}