Block size comes from the mounted filesystem (fs_statvfs()), which on ATT targets uses external SPI-NOR with CONFIG_SPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096 (0x1000). The table below illustrates minimal sizing for a small configuration (three data types, eight records per type); the shipped default is 1 MiB with up to 256 records per type, which needs far more blocks—the LittleFS backend checks sizing at init (see the LittleFS partition size verified log line) or use the formula above.
| Target | Block size | Example blocks needed | Example minimal partition |
|---|---|---|---|
| nrf9151 DK / Thingy:91 X (external SPI-NOR) | 0x1000 (4096 B) | 8 + 3 metadata | 0x2c000 (~176 KiB) |
| Internal flash (not recommended) | 0x1000 | 8 + 3 metadata | 0x2c000 |
The default 1 MiB (0x00100000) partition on both boards leaves ample margin for all enabled data types at CONFIG_APP_STORAGE_MAX_RECORDS_PER_TYPE=256.