The test_onefile.c VFS provides the barest VFS, without locking support, just like unix-none. I cannot tell from your initial post (or any other) whether your use cases include multi-threaded or possibly reentrant access. Neither starting point does anything with locking calls, which dooms multi-threaded use cases unless you arrange your own locking outside of the library. For mere file I/O, both are trivially easy to adapt for a different set of underlying APIs, so I think your concern with "easier" may be misplaced. I would be concerned also with write and rewrite performance. SD storage devices can fail quickly if the system using them keeps rewriting the same block a lot. (I speak as a student of the hard knocks school on this.) You might, depending on the application, do well keep the DB in fast, durable memory and use a cache flushing strategy to reduce wear on the SD memory. That would also largely bypass the speed issues with SD memory devices.