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<title>Understanding enabled and disabled read-ahead cache mode for logical devices</title>

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<h1>Understanding enabled and disabled read-ahead cache mode for logical devices</h1>

<h2>Enabled read-ahead cache mode </h2>
<p>The controller transfers data from the logical device to its local
  cache in increments equal to the stripe size. This provides excellent overall
  performance when workloads are steady and sequential. However, if the workload
  is random or the system I/O requests are smaller than the stripe size,
  reading ahead to the end of the stripe might degrade performance. </p>
<h2>Disabled read-ahead cache mode </h2>
<p>The controller transfers data from the logical device to its local
  cache in increments equal to the system I/O request size, without reading ahead
  to the end of the stripe. This provides excellent overall performance when the
  workload is random or the system I/O requests are smaller than the stripe
  size.</p>
<h2>More information</h2>
<ul>
  <li><a href="aracache.htm">Enabling and disabling read-ahead cache mode (action)</a></li>
  <li><a href="wadvstcc.htm">Changing the stripe size</a></li>
  <li><a href="cstripe.htm">Understanding stripe size</a></li>
</ul>

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