title: High Number of MySQL Temporary Disk Tables
body: <p>We have noticed that MySQL is reporting a very high number of temporary disk tables (over 10,000) this is reported by <a href="http://serverdensity.com" rel="noreferrer">Server Density</a>. Were trying to understand a bit more about this.</p>
  
  <ul>
  <li>Why are temporary disk tables created by MySQL? </li>
  <li>What impact do they have on performance?</li>
  <li>Are they ever removed by MySQL or will this number just increase?</li>
  </ul>