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I need to create a new file handle so that any write operations to that handle get written to disk immediately. Extra info: The handle will be the inherited STDOUT of a child process, so I need any output from that process to immediately be written to disk. Studying the CreateFile documentation, the FILE_FLAG_WRITE_THROUGH flag looked like exactly what I need: Write operations will not go through any intermediate cache, they will go directly to disk. I wrote a very basic test program and, well, it's not working. I used the flag on CreateFile then used WriteFile(myHandle,...) in a long loop, writing about 100MB of data in about 15 seconds. (I added some Sleep() 's). I then set up a professional monitoring environment consisting of continuously hitting 'F5' in explorer. The results: the file stays at 0kB then jumps to 100MB about the time the test program ends. Next thing I tried was to manually flush the file after each write, with FlushFileBuffers(myHandle) . This makes the observed file size grow nice and steady, as expected. My question is, then, shouldn't the FILE_FLAG_WRITE_THROUGH have done this without manually flushing the file? Am I missing something? In the 'real world' program, I can't flush the file, 'cause I don't have any control over the child process that's using it. There's also the FILE_FLAG_NO_BUFFERING flag, that I can't be used for the same reason - no control over the process that's using the handle, so I can't manually align the writes as required by this flag. EDIT: I have made a separate project specifically for watching how the size of the file changes. It uses the .NET FileSystemWatcher class. I also write less d

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