hesela.devNAND spare area
The additional region associated with a NAND page, used for error-correction information, bad-block markers and other metadata according to a device- and controller-specific layout.
OOB means out-of-band relative to the page's main data, not a separate management bus. Linux MTD distinguishes ECC positions, reserved bad-block information and regions available for filesystem metadata; available bytes need not form one contiguous range. [1]
Do not treat this as SSD over-provisioning or replacement blocks. It is per-page storage, and ECC requirements can constrain the space left for an FTL. [2]
For a raw-NAND image or boot-chain migration, record the page geometry, ECC scheme and OOB layout together. Preserve factory bad-block markers and follow the part's programming restrictions. A data-only dump does not by itself specify these details. This checklist is an engineering inference from the documented layout responsibilities. [1]
Relations
- related
- nand-flash, nand-page, nand-erase-block, error-correcting-code, bad-block-management, ftl, over-provisioning
Limitations
- A documented OOB layout is not a universal offset map for other NAND parts or controllers. [1]
Citations
- Linux kernel. MTD NAND Driver Programming Interface: Bad block table support; Spare area (auto)placement; Filesystem support.
- Peter Desnoyers. What Systems Researchers Need to Know about NAND Flash. HotStorage 2013, section 3, Page spare areas.
Sources & caveats
- Source review. The kernel document contains legacy API examples; this entry uses layout concepts, not its example byte offsets, page sizes or partial-program counts as current universal requirements. No device imaging or power-loss experiment was performed.
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Hesela team. NAND spare area. Hesela. 2026-10-18. https://hesela.dev/terms/nand-spare-area/