This has almost nothing to do with Java and there is nothing revealing in this blog post. Block device operations on Linux always went through layers of indirec

This has almost nothing to do with Java and there is nothing revealing in this blog post. Block device operations on Linux always went through layers of indirection. That's why things like page cache or writeback exist. You can always go O_DIRECT if you need the write to be truly synchronous. If anything the author just discovered how IO works on Linux.