191 lines
9.0 KiB
HTML
191 lines
9.0 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xml:lang="en" lang="en" xmlns="http://www.w3.org/1999/xhtml">
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<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
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<meta http-equiv="Content-Style-Type" content="text/css" />
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<title>About Degraded Units</title>
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<link rel="StyleSheet" href="css/Maintain_Units.css" type="text/css" media="all" />
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<body style="">
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<a href="http://www.lsi.com/channel/products" target="_blank">
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</table>
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<div style="text-align: left;">
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<p style="color: Navy; font-weight:bold">3DM2™ Online
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Help</p>
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<a href="toc.html">
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<div class="WebWorks_Breadcrumbs" style="text-align: left;">
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<a class="WebWorks_Breadcrumb_Link" href="Maintain_Units.7.1.html#1145155">Maintaining Units</a> > About Degraded Units</div>
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<hr align="left" />
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<div>
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<div class="Heading1"><a name="1145155">About Degraded Units</a></div>
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<div class="Body"><a name="1169358">Fault-tolerant RAID units provide data redundancy by duplicating </a>information on multiple drives. These RAID units make it possible to continue use even if one of the drives in the unit has failed. </div>
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<div class="Bullet_outer" style="margin-left: NaN;">
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<div class="Bullet_inner"><a name="1169359">RAID 1 and RAID 10 units each use mirroring to achieve fault tolerance. </a>Identical data is stored on two or more drives to protect against drive failure.</div>
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<div class="Bullet_inner"><a name="1431585">RAID 5, RAID 6, and RAID 50 units achieve fault tolerance by using a </a>simple (exclusive OR) function to generate the parity data that is distributed on all drives. </div>
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<div class="Bullet_inner"><a name="1431590">RAID 6 adds an extra level of protection over RAID 5 by generating a </a>second parity when data is written. This allows two drives to fail without compromising data integrity, especially on larger units. </div>
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</td>
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</table>
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</div>
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<div class="Body"><a name="1322640">When one of the drives in a fault-tolerant unit fails or is removed or </a>unplugged, the unit is said to be <span class="Emphasis">degraded</span>. </div>
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<div class="Body"><a name="1169383">You can still read and write data from a degraded unit, but the unit will not be </a>fault tolerant until it is rebuilt using the Rebuild feature. </div>
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<div class="Body"><a name="1363321">When a RAID unit becomes degraded, it is marked as such, and the drive(s) </a>that failed are marked as <span class="UI-Element">Degraded</span> in the 3DM2 pages. If supported by your enclosure, the LED for failed drives may turn red.</div>
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<div class="Body"><a name="1170795">You should replace the failed drive and rebuild the unit as soon as it is </a>convenient to do so. The unit will not be fault tolerant until it has been rebuilt. Rebuilding can occur automatically, depending on your settings. For more information, see <a href="Maintain_Units.7.20.html#1353024">Rebuilding Units</a>. </div>
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<hr />
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<dl>
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<dt>Related Topics</dt>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.2.html#1080998" name="1675214">Checking Unit and Drive Status</a></div>
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</dd>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.4.html#1486727" name="1675218">Enclosure Drive LED Status Indicators</a></div>
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</dd>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.5.html#1251822" name="1675222">Unit Statuses</a></div>
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</dd>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.6.html#1145546" name="1675226">Drive Statuses</a></div>
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</dd>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.11.html#1304943" name="1675230">Viewing Alarms, Errors, and Other Events</a></div>
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</dd>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.13.html#1136387" name="1675234">Downloading an Error Log</a></div>
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</dd>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.14.html#1079505" name="1675238">Viewing SMART Data About a Drive</a></div>
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</dd>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.8.html#1258376" name="1675242">About Inoperable Units</a></div>
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</dd>
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<dd>
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<div class="RelatedTopic"><a href="Maintain_Units.7.20.html#1353024" name="1675246">Rebuilding Units</a></div>
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</dd>
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</dl>
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</div>
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<hr align="left" />
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<div style="text-align: left;">
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<table cellspacing="0">
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<tr>
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<td>
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<a href="toc.html">
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<img src="images/toc.gif" alt="Table of Contents" border="0" />
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</a>
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</td>
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<td>
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<a href="Maintain_Units.7.6.html">
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<img src="LSI-logo.jpg" border="0" />
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<td style="text-align: left; font-size: 16px ; font-weight: bold">
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<a href="http://www.lsi.com/channel/products" target="_blank">LSI Corporation</a>
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</tr>
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</table>
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<p style="font-size: .8em">Copyright LSI 2004-2010<br />
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To contact Support, go to <a href="http://www.lsi.com/channel/ContactUs">http://www.lsi.com/channel/ContactUs</a></p>
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</html>
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