{
  "slug": "zoned-bit-recording",
  "term": "Zoned bit recording (ZBR)",
  "aliases": [
    "ZBR",
    "zone bit recording"
  ],
  "definition": "Zoned bit recording groups HDD tracks into radial zones with different sector counts per track, typically assigning more sectors to outer tracks.",
  "note": "Longer outer tracks can hold more sectors per revolution. Recording frequency varies between zones; this does not require changing spindle speed between zones. Linear recording density measures bits per unit track length, rather than the zone layout. [zbr-frequency]\n\nWithin a recording zone containing S payload sectors per track, with B payload bytes per sector and fixed RPM, S x B x RPM / 60 gives an idealized payload rate in bytes/s for one head. Track/head switches, seeks, retries and other workload costs affect sustained host throughput. [hdd-card]\n\nThese recording zones are distinct from the host-facing zones of zoned block devices and ZNS namespaces, which define access and management rules. ZBR alone specifies neither a write pointer nor a reset requirement. [zoned-overview]\n\nHistorical SCSI Notch mode pages could report recording-zone boundaries. A reported geometry is not itself a sequential-write-required zone contract. [zbr-notch]\n\nThe ST3655 manual's average sectors per track is not a zone-local S for the rate formula. Verify the reporting scope before using a geometry field as a physical-layout measurement. [zbr-notch]\n\nIn the ST3655 Format Device page (03H), Tracks per zone describes defect-management groups, not recording-zone width. The Notch page (0CH) describes recording zones separately. [zbr-notch]\n\nThat Notch page uses LPN = 0, so boundaries are cylinder/head coordinates, not logical block addresses. Active notch = 0 selects parameters for all notches rather than one individual notch. [zbr-notch]",
  "status": "unknown",
  "advantages": [],
  "limitations": [],
  "related": [
    "hdd",
    "linear-recording-density",
    "track-density",
    "areal-density",
    "zoned-block-device",
    "hm-smr",
    "zns",
    "track-skew"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "zbr-notch",
      "title": "Seagate: ST3655 Family SCSI Product Manual, Rev. A, 18 January 1994, sections C.3 and C.7, pp. 96-98 and 108-109",
      "url": "https://www.seagate.com/support/disc/manuals/scsi/3655npmb.pdf",
      "accessed": "2026-10-24"
    },
    {
      "id": "zbr-frequency",
      "title": "Leow et al.: Adaptive zone frequency compensation for disc drives, US6757119B2 (2004), Background of the Invention",
      "url": "https://patents.google.com/patent/US6757119B2/en",
      "accessed": "2026-10-23"
    },
    {
      "id": "zoned-overview",
      "title": "Western Digital, Zoned Storage: device models, zone types and management commands",
      "url": "https://zonedstorage.io/docs/introduction/zoned-storage",
      "accessed": "2026-10-23"
    },
    {
      "id": "hdd-card",
      "title": "Hesela: Hard Disk Drive, density and transfer-rate interpretation",
      "url": "https://hesela.com/tech/hdd/",
      "accessed": "2026-10-23"
    }
  ],
  "updated": "2026-10-24",
  "provenance": [
    "The 1994 Seagate manual documents an implemented format and SCSI reporting behavior; it does not establish ZBR's invention date. [zbr-notch]",
    "The patent's technical background describes zone-dependent recording frequency, not a universal modern-drive layout or speed ratio. [zbr-frequency]"
  ]
}