flashbench

Well, there's still flashbench: https://github.com/bradfa/flashbench Plus, alternatively, there's FlashBench: https://github.com/JonghyeokPark/FlashBench These might be found useful for determining the underlying structure.

Once upon a time, Linaro produced flashbench, a tool for learning more information about how managed NAND devices (mmc, sdcard, etc) actually manage their flash. LWN did a story on some of their conclusions [1]. One of the standouts for me was that some erase blocks are managed completely differently from others, such that random i/o performance can vary based on the location on the device. Traditional filesystem benchmarks aren't set up to observe this behavior. IIUC, F2FS incorporated some of that information, and not much else has. But in principle, you should manage your device with short extents and inode tables in the small-block-friendly area, and larger extents elsewhere whenever possible. [0]: https://github.com/bradfa/flashbench [1]: https://lwn.net/Articles/428584/

For some reason I cannot reply to your message directly, only to a parent. Flashbench [1] should be able to tell you what the erase-block and page size is. [1] https://github.com/bradfa/flashbench