title: multiple writes on a writestream in node.js
body: <p>I've been looking at the code of node-dirty and noticed that when writing a lot of data to a file, the original programmer has chosen to bunch the writes into several groups and issue writes of the groups one at a time, but they are all issued simultaneously as part of one loop, without waiting for any callbacks. I have three questions about this. I have a similar problem to solve.</p>
  
  <ol>
  <li>Is this more efficient in some way? Should I be bundling writes too? </li>
  <li>How should I choose the optimum bundle size? Why not just write one group?</li>
  <li>If I sign up to the on('drain') event on the writestream, will it be emitted only once after all the simultaneously issued writes have completed? Or after each? (my guess is the former)</li>
  <li>If the on('error') is emitted, will the ('drain') event also be emitted? Or are they mutually exclusive?</li>
  </ol>
  
  <p>thanks </p>