title: ext4 commit= mount option and dirty_writeback_centisecs
body: <p>I'm tring to understand the way bytes go from write() to the phisical disk plate to tune my picture server performance.</p>
  
  <p>Thing I don't understand is what is the difference between these two: <strong>commit=</strong> mount option and <strong>dirty_writeback_centisecs</strong>. Looks like they are about the same procces of writing changes to the storage device, but still different.</p>
  
  <p>I do not get it clear which one fires first on the way to the disk for my bytes.</p>