hesela.devNVMe extended LBA
An NVMe extended LBA is a transfer layout in which each logical block's data is immediately followed by its metadata.
nvme-cli v2.11 exposes metadata placement through --ms: 1 selects an extended data LBA and 0 a separate metadata buffer. Here --ms selects placement, not a byte count. Its --pi option separately selects whether protection information is enabled and which type is used. Metadata can include PI without being synonymous with it. Formatting is potentially destructive, not a read-only inspection. [2]
With PI enabled and metadata consisting entirely of PI, PRACT=1 inserts PI on writes and strips it on reads. With additional metadata, writes replace the PI portion and reads retain it instead. Transfer length therefore cannot be inferred from the placement setting alone. [1]
The transfer layout does not establish application-to-device protection. Linux can generate integrity metadata below the application; identify the generation and verification points. [3]
MC and DPC report capabilities. FLBAS identifies the selected format and transfer layout; that format's LBAF.MS gives metadata bytes per LBA, and DPS reports the enabled PI type. These namespace fields do not report a command's PRACT or PRCHK. [1]
In NVM Command Set 1.0e, 16b Guard PI occupies 8 bytes; 32b and 64b Guard PI occupy 16 bytes. Guard width is not total PI size. When metadata exceeds PI size, PRACT=1 still transfers all metadata bytes: writes replace the PI portion, while reads return it after applicable checks. [1]
Relations
Citations
- NVM Command Set 1.0e: Figures 9, 78; Figures 97 and 98; 5.2.2. Copyright 2008 to 2024 NVM Express, Inc. ALL RIGHTS RESERVED.
- nvme-cli v2.11: Format NVM metadata placement, PI options and destructive-operation warning
- Linux v6.12 Data Integrity documentation, sections 3 and 5 (historical design context)
Further reading
Sources & caveats
- Version-scoped specification and tool-documentation review, not a controller experiment or a driver-support matrix.
- Extended LBA describes transfer arrangement; extended protection information describes additional PI formats. They are not synonyms.
- Identify Namespace field review: section 4.1.5.1, Figure 97 pp. 58-59 and Figure 98 pp. 64-65. CLI --ms means placement; LBAF.MS means metadata bytes.
- PI sizes: sections 5.2.1.1 to 5.2.1.3, Figures 114 to 118 (pp. 78 to 81). PRACT transfer rules: sections 5.2.2.1 and 5.2.2.2 (pp. 89 to 91); checking exceptions: section 5.2.3.