title: Scaling in Windows Azure for IO Performance
body: <p>Windows Azure advertises three types of IO performance levels:</p>
  
  <ul>
  <li>Extra Small : Low</li>
  <li>Small: Moderate</li>
  <li>Medium and above: High</li>
  </ul>
  
  <p>So, if I have an IO bound application (rather than CPU or Memory bound) and need at least 6 CPUs to process my work load - will I get better IO performance with 12-15 Extra Smalls, 6 Smalls, or 3 Mediums?</p>
  
  <p>I'm sure this varies based on applications - is there an easy way to go about testing this? Are there any numbers that give a better picture of how much of an IO performance increase you get as you move to large instance roles?</p>
  
  <p>It seems like the IO performance for smaller roles could be equivalent to the larger ones, they are just the ones that get throttled down first if the overall load becomes too great. Does that sound right?</p>