zoned-bit-recording · unknown · also ZBR, zone bit recording

Zoned bit recording (ZBR)

Zoned bit recording groups HDD tracks into radial zones with different sector counts per track, typically assigning more sectors to outer tracks.

Related Observatory article: Zoned bit recording (ZBR) on hesela.com

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. [2]

Within 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. [4]

These 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. [3]

Historical SCSI Notch mode pages could report recording-zone boundaries. A reported geometry is not itself a sequential-write-required zone contract. [1]

The 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. [1]

In 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. [1]

That 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. [1]

Relations

related

Hard disk drive (HDD), Linear recording density, Track density, Areal density, Zoned block device (ZBD), Host-managed SMR (HM-SMR), Zoned namespaces (ZNS), Track skew

Citations

1. Seagate: ST3655 Family SCSI Product Manual, Rev. A, 18 January 1994, sections C.3 and C.7, pp. 96-98 and 108-109 (accessed 2026-10-24)
2. Leow et al.: Adaptive zone frequency compensation for disc drives, US6757119B2 (2004), Background of the Invention (accessed 2026-10-23)
3. Western Digital, Zoned Storage: device models, zone types and management commands (accessed 2026-10-23)
4. Hesela: Hard Disk Drive, density and transfer-rate interpretation (accessed 2026-10-23)

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