95 lines
6.2 KiB
HTML
95 lines
6.2 KiB
HTML
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Extended Adaptive Cache Concepts" />
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<meta name="abstract" content="Explore Extended Adaptive Cache. Find information about planning, restrictions, and important considerations before you begin to use this tool." />
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<meta name="description" content="Explore Extended Adaptive Cache. Find information about planning, restrictions, and important considerations before you begin to use this tool." />
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<title>Extended Adaptive Cache Concepts</title>
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<body id="rzahxeac1"><a name="rzahxeac1"><!-- --></a>
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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">Extended Adaptive Cache Concepts</h1>
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<div><p>Explore Extended Adaptive Cache. Find information about planning,
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restrictions, and important considerations before you begin to use this tool.</p>
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<p>Improve system performance with Extended Adaptive Cache, an advanced read
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cache technology that improves both the I/O subsystem and system response
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times by reducing the number of physical I/O requests that are read from disk.
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Extended Adaptive Cache not only improves the performance of database-read
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actions, but of all read actions. This includes read actions that are generated
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by other system components such as the <span class="keyword">Integrated xSeries<sup>®</sup> Server</span>.
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It also works effectively in storage subsystems that have device parity protection
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or mirrored protection. Extended Adaptive Cache has proven to be highly effective
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on many types of workloads.</p>
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<div class="section"><h4 class="sectiontitle">How the Extended Adaptive Cache works</h4><p>Extended Adaptive
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Cache is integrated into the <span class="keyword">iSeries™</span> I/O
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subsystem. It operates at the disk subsystem controller level and does not
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affect the <span class="keyword">iSeries</span> system processor.
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The storage I/O adapter manages the Extended Adaptive Cache by using a Read
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Cache Device (such as a solid state disk) to provide the cache memory.</p>
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<p>Extended
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Adaptive Cache generates statistical information for the data, and then uses
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a mix of management strategies to determine which data to cache. The management
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of the cache is performed automatically within the I/O adapter and is designed
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to cache data by using a predictive algorithm. The algorithm considers how
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recently and how frequently the host has accessed a predetermined range of
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data.</p>
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<p>The design of Extended Adaptive Cache was based on specific data
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management strategies of the <span class="keyword">iSeries</span> server.
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Whether the disks are device parity protected, mirrored, or unprotected, the
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data stored on the disks has a tendency to occur in bands. This means that
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there are physically contiguous areas of disk storage where data is actively
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read, physically contiguous areas that are frequently written to, physically
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contiguous areas that are both actively read and written to, or physically
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contiguous areas of storage that are not frequently accessed.</p>
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<p>This "banding"
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of data is accounted for in the Extended Adaptive Cache design. The goal is
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to cache bands characterized as read/write and read-only. A band that is characterized
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as write-only, while cached in the storage subsystem write cache, remains
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largely unaffected by Extended Adaptive Cache. Extended Adaptive Cache is
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also designed to not harm the performance of large blocks of data that are
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either sequentially written or sequentially read. In this instance, the pre-fetch
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capability of the disks, as well as other caches in the system, ensures a
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quick response time.</p>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rzahxeacplan.htm">Restrictions and considerations for Extended Adaptive Cache</a></strong><br />
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See what components Extended Adaptive Cache requires and learn more about what to expect.</li>
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<li class="ulchildlink"><strong><a href="rzahxeacuse.htm">Start Extended Adaptive Cache</a></strong><br />
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To start Extended Adaptive Cache and increase your system's performance, purchase the Read Cache Device.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzahxintro.htm" title="You can use Extended Adaptive Cache to improve system performance by collecting disk usage data, and then using those statistics to create a cache, effectively reducing the physical I/O requests for the disk.">Extended Adaptive Cache</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="../rzalm/rzalmlvm.htm">Device parity protection</a></div>
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<div><a href="../rzaly/rzalymirrorconcept.htm">Mirrored protection</a></div>
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</div>
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</div>
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</body>
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</html>
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