title: I/O Disk Drive Calculations
body: <p>So I am studying for an up and coming exam, one of the questions involves calculating various disk drive properties. I have spent a fair while researching sample questions and formula but because I'm a bit unsure on what I have come up with I was wondering could you possibly help confirm my formulas / answers?</p>
  
  <p><b>Information Provided:</b></p>
  
  <p>Rotation Speed = 6000 RPM<br /> 
  Surfaces = 6<br />
  Sector Size = 512 bytes<br />
  Sectors / Track = 500 (average)<br />
  Tracks / Surfaces = 1,000<br />
  Average Seek Time = 8ms<br />
  One Track Seek Time = 0.4 ms<br />
  Maximum Seek Time = 10ms</p>
  
  <p><b>Questions:</b></p>
  
  <p>Calculate the following</p>
  
  <p>(i) The capacity of the disk<br />
  (ii) The maximum transfer rate for a single track<br />
  (iii) Calculate the amount of cylinder skew needed (in sectors)<br />
  (iv) The Maximum transfer rate (in bytes) across cylinders (with cylinder skew)</p>
  
  <p><b>My Answers:</b></p>
  
  <p><b>(i)</b>  Sector Size x Sectors per Track x Tracks per Surface x No. of surfaces</p>
  
  <p>512 x 500 x 1000 x 6 = 1,536,000,000 bytes </p>
  
  <p><b>(ii)</b> Sectors per Track x Sector Size x Rotation Speed per sec</p>
  
  <p>500 x 512 x (6000/60) = 25,600,000 bytes per sec</p>
  
  <p><b>(iii)</b> (Track to Track seek time / Time for 1 Rotation) x Sectors per Track + 4</p>
  
  <p>(0.4 / 0.1) x 500 + 4 = 24</p>
  
  <p><b>(iv)</b>  Really unsure about this one to be honest, any tips or help would be much appreciated.</p>
  
  <p>I fairly sure a similar question will appear on my paper so it really would be a great help if any of you guys could confirm my formulas and derived answers for this sample question. Also if anyone could provide a bit of help on that last question it would be great.</p>
  
  <p>Thanks.</p>