Doesn't matter. Even a log-structured fs, when told to write 4 bytes of new data to disk will have to write those 4 bytes immediately and return. If an applicat

Doesn't matter. Even a log-structured fs, when told to write 4 bytes of new data to disk will have to write those 4 bytes immediately and return. If an application asks the OS (via fsync), and the OS asks the fs and the fs doesn't write to disk but tells the OS it did, then the fs just lied and risked data loss. If power is lost between the fs lying to the OS and its subsequently actually writing to disk, the data that the fs lied about is lost. You don't want that with a DB on top of it.