hesela.devNVMe atomic boundary
An NVMe atomic boundary is a namespace address boundary that constrains the scope of namespace atomic-write guarantees.
NABSN applies to normal operation, NABSPF to interrupted writes, and NABO gives the starting LBA offset. A zero boundary-size field means no corresponding boundary; nonzero sizes encode logical-block counts minus one. This differs from NAWUN or NAWUPF zero, which inherits a controller unit. [2] [1]
In Single Atomicity Mode, crossing a boundary can remove the larger namespace guarantee. It does not cancel the controller AWUN/AWUPF baseline: those reported sizes must work across boundaries. A size limit alone is therefore insufficient when relying on a namespace-specific guarantee. [1]
Multiple Atomicity Mode divides a spanning command into separately atomic LBA subranges. It does not make those subranges a single all-or-nothing update. Record the namespace format, unit fields, boundary fields and selected mode together; formatting can change the namespace parameters. [1]
Relations
Limitations
- Separately atomic subranges do not form a single atomic transaction spanning the command. [1]
Citations
- NVM Express NVM Command Set 1.3 (2026): sections 2.1.4, 3.3.6 and 4.1.3.4; Figures 123 and 126. Copyright 2008-2026 NVM Express, Inc. All rights reserved.
- Microsoft: NVME_IDENTIFY_NAMESPACE_DATA, namespace atomic unit and boundary encodings
Sources & caveats
- Source synthesis pinned to NVM Command Set 1.3; no hardware test, crash experiment or performance measurement.