57 lines
3.9 KiB
HTML
57 lines
3.9 KiB
HTML
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<title>Elements of device parity protection</title>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Elements of device parity protection</h1>
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<div><p>The following diagrams illustrate the elements of a parity set that contains
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four disk units. Each parity set begins with an input/output processor (IOP)
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that is attached to an input/output adapter (IOA), which contains the write
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cache. The IOA transmits read and write signals to the attached disk units. </p>
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<p><em>P</em> indicates the sections of the disk that contain parity
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data. </p>
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<div class="p"><em>Q</em> indicates the second stripe of parity data.<div class="note"><span class="notetitle">Note:</span> The
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second stripe of parity data is only associated with RAID 6 protection.</div>
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</div>
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<div class="fignone"><span class="figcap">Figure 1. Example of how parity data is distributed with RAID
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5 pre-V5R2 IOAs</span><br /><img src="rzaix518.gif" alt="RAID 5 parity
data is spread across four disk units. The parity set has an input/output
processor (IOP) that is attached to an input/output adapter (IOA), which contains
the write cache." /><br /></div>
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<div class="fignone"><span class="figcap">Figure 2. Example of how parity data is distributed with RAID
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5 post-V5R2 IOAs</span><br /><img src="rzaix521.gif" alt="RAID 5 parity
data is spread across four disk units. The parity set has an input/output
processor (IOP) that is attached to an input/output adapter (IOA), which contains
the write cache." /><br /></div>
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<p>Performance is improved by spreading the parity data throughout
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each of the disk units. The device parity protection that is spread throughout
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the disk units equals one disk unit of memory. </p>
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<div class="fignone"><span class="figcap">Figure 3. Example of how parity data is distributed with RAID
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6</span><br /><img src="rzaix525.gif" alt="RAID 6 parity
data is spread across four disk units. The parity set has an input/output
processor (IOP) that is attached to an input/output adapter (IOA), which contains
the write cache." /><br /></div>
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<p>Performance is improved by spreading the parity throughout
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each of the disk units. The total amount of protection that is spread throughout
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the disk units equals two disk units of memory. </p>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalydpp.htm">Device parity protection</a></div>
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