title: How is Average Seek Time Calculated?
body: <p>A hard disk system has the following parameters :</p>
  
  <pre><code>Number of tracks = 500
  Number of sectors/track = 100
  Number of bytes /sector = 500
  Time taken by the head to move from one track to adjacent track = 1 ms
  Rotation speed = 600 rpm.
  </code></pre>
  
  <p>What is the average time taken for transferring 250 bytes from the disk ?</p>
  
  <p>Well I wanted to know <strong>How the average seek time is calculated ?</strong></p>
  
  <p><strong>My Approach</strong></p>
  
  <p>Avg. time to transfer = Avg. seek time + Avg. rotational delay + Data transfer time</p>
  
  <p><strong>Avg Seek Time</strong></p>
  
  <p>given that : time to move between successive tracks is 1 ms</p>
  
  <p>time to move from track 1 to track 1 : 0ms</p>
  
  <p>time to move from track 1 to track 2 : 1ms</p>
  
  <p>time to move from track 1 to track 3 : 2ms</p>
  
  <p>..</p>
  
  <p>..</p>
  
  <p>time to move from track 1 to track 500 : 499 ms</p>
  
  <p>Avg Seek time =<a href="https://i.stack.imgur.com/BYr9b.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BYr9b.gif" alt="enter image description here"></a>
                           = 249.5 ms</p>
  
  <p>But After Reading Answer given here  <a href="https://stackoverflow.com/questions/9828736">Why is average disk seek time one-third of the full seek time?</a></p>
  
  <p>Im confused with my approach.  </p>
  
  <p><strong>My question is</strong> </p>
  
  <p>Is my Approach Correct ?</p>
  
  <ul>
  <li>If not Please explain the correct way to calculate Average seek time</li>
  <li>If Yes please explain wh we are not considering average for every possible pair of tracks (as mentioned in the above link)? </li>
  </ul>