146 lines
9.7 KiB
HTML
146 lines
9.7 KiB
HTML
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Tunable cluster communications parameters" />
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<meta name="abstract" content="The Change Cluster Resource Services (QcstChgClusterResourceServices) API enables some of the cluster topology services and cluster communications performance and configuration parameters to be tuned to better suit the many unique application and networking environments in which clustering occurs. This API is available to any cluster that is running at cluster version 2 or later." />
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<meta name="description" content="The Change Cluster Resource Services (QcstChgClusterResourceServices) API enables some of the cluster topology services and cluster communications performance and configuration parameters to be tuned to better suit the many unique application and networking environments in which clustering occurs. This API is available to any cluster that is running at cluster version 2 or later." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Identifier" content="rzaigmanagetunablecommparameters" />
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<title>Tunable cluster communications parameters</title>
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</head>
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<body id="rzaigmanagetunablecommparameters"><a name="rzaigmanagetunablecommparameters"><!-- --></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">Tunable cluster communications parameters</h1>
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<div><p>The <span class="apiname">Change Cluster Resource Services (QcstChgClusterResourceServices)</span> API
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enables some of the cluster topology services and cluster communications performance
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and configuration parameters to be tuned to better suit the many unique application
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and networking environments in which clustering occurs. This API is available
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to any cluster that is running at cluster version 2 or later.</p>
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<p>The <a href="../cl/chgclucfg.htm"><span class="cmdname">Change
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Cluster Configuration Tuning (CHGCLUCFG)</span> command</a> provides
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a base level of tuning, while the <a href="../apis/clcntchgcrs.htm"><span class="apiname">QcstChgClusterResourceServices</span> API </a>provides
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both base and advanced levels of tuning.</p>
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<p>The <span class="apiname">QcstChgClusterResourceServices</span> API and <span class="cmdname">CHGCLUCFG</span> command
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can be used to tune cluster performance and configuration. The API and command
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provide a base level of tuning support where the cluster will adjust to a
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predefined set of values identified for high, low, and normal timeout and
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messaging interval values. If an advanced level of tuning is desired, usually
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anticipated with the help of IBM<sup>®</sup> support personnel, then individual parameters may
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be tuned through use of the API over a predefined value range. Inappropriate
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changes to the individual parameters can easily lead to degraded cluster performance.</p>
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<div class="section"><h4 class="sectiontitle">When and how to tune cluster parameters?</h4><p>The <span class="cmdname">CHGCLUCFG</span> command
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and the <span class="apiname">QcstChgClusterResourceServices</span> API provide for
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a fast path to setting cluster performance and configuration parameters without
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your needing to understand details. This base level of tuning primarily affects
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the heartbeating sensitivity and the cluster message timeout values. The valid
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values for the base level of tuning support are:</p>
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<p>1 (High Timeout Values/Less
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Frequent Heartbeats)</p>
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<dl><dt class="dlterm">2 (Default Values)</dt>
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<dd>Normal default values are used for cluster communications performance
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and configuration parameters. This setting may be used to return all parameters
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to the original default values. </dd>
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<dt class="dlterm">3 (Low Timeout Values / More Frequent Heartbeats)</dt>
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<dd>Adjustments are made to cluster communications to decrease the heartbeating
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interval and decrease the various message timeout values. With more frequent
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heartbeats and shorter timeout values, the cluster is quicker to respond (more
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sensitive) to communications failures.</dd>
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</dl>
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<p>Resultant example response times are shown in the following
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table for a heartbeat failure leading to a node partition:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><thead align="left"><tr><th valign="top" id="d0e84"> </th>
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<th colspan="3" valign="top" id="d0e85">1 (Less sensitive)</th>
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<th colspan="3" valign="top" id="d0e87">2 (Default)</th>
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<th colspan="3" valign="top" id="d0e89">3 (More sensitive)</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e84 "> </td>
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<td valign="top" headers="d0e85 ">Detection of Heartbeat Problem</td>
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<td valign="top" headers="d0e85 ">Analysis</td>
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<td valign="top" headers="d0e85 ">Total</td>
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<td valign="top" headers="d0e87 ">Detection of Heartbeat Problem</td>
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<td valign="top" headers="d0e87 ">Analysis</td>
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<td valign="top" headers="d0e87 ">Total</td>
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<td valign="top" headers="d0e89 ">Detection of Heartbeat Problem</td>
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<td valign="top" headers="d0e89 ">Analysis</td>
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<td valign="top" headers="d0e89 ">Total</td>
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</tr>
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<tr><td valign="top" headers="d0e84 ">Single subnet</td>
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<td valign="top" headers="d0e85 ">00:24</td>
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<td valign="top" headers="d0e85 ">01:02</td>
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<td valign="top" headers="d0e85 ">01:26</td>
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<td valign="top" headers="d0e87 ">00:12</td>
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<td valign="top" headers="d0e87 ">00:30</td>
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<td valign="top" headers="d0e87 ">00:42</td>
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<td valign="top" headers="d0e89 ">00:04</td>
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<td valign="top" headers="d0e89 ">00:14</td>
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<td valign="top" headers="d0e89 ">00:18</td>
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</tr>
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<tr><td valign="top" headers="d0e84 ">Multiple subnets</td>
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<td valign="top" headers="d0e85 ">00:24</td>
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<td valign="top" headers="d0e85 ">08:30</td>
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<td valign="top" headers="d0e85 ">08:54</td>
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<td valign="top" headers="d0e87 ">00:12</td>
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<td valign="top" headers="d0e87 ">04:14</td>
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<td valign="top" headers="d0e87 ">04:26</td>
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<td valign="top" headers="d0e89 ">00:04</td>
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<td valign="top" headers="d0e89 ">02:02</td>
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<td valign="top" headers="d0e89 ">02:06</td>
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</tr>
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</tbody>
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</table>
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</div>
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<div class="note"><span class="notetitle">Note:</span> <img src="./delta.gif" alt="Start of change" />Times are specified in minutes:seconds format.<img src="./deltaend.gif" alt="End of change" /></div>
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<p>Depending
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on typical network loads and specific physical media being used, a cluster
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administrator might choose to adjust the heartbeating sensitivity and message
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timeout levels. For example, with a high speed high-reliability transport,
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such as OptiConnect with all systems in the cluster on a common OptiConnect
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bus, one might desire to establish a more sensitive environment to ensure
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quick detection leading to faster failover. Option 3 is chosen. If one were
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running on a heavily loaded 10Mbs Ethernet bus and the default settings were
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leading to occasional partitions just due to network peak loads, option 1
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could be chosen to reduce clustering sensitivity to the peak loads.</p>
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<p>The
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Change Cluster Resource Services API also allows for tuning of specific individual
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parameters where the network environmental requirements present unique situations.
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For example, consider again a cluster with all nodes common on an OptiConnect
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bus. Performance of cluster messages can be greatly enhanced by setting the
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Message Fragment Size parameter to the maximum 32,500 bytes to better match
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the OptiConnect Maximum Transmission Unit (MTU) size than does the default
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1,464 bytes. This reduces the overhead of fragmentation and reassembly of
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large messages. The benefit, of course, depends on the cluster applications
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and usage of cluster messaging resulting from those applications. Other parameters
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are defined in the API documentation and may be used to tune either the performance
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of cluster messaging or change the sensitivity of the cluster to partitioning.</p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaigplan.htm" title="Find out what you need to do before you can set up clusters on your iSeries servers. Find out the prerequisites for clusters as well as hints on designing your cluster. Finally, read tips for setting up your network and some performance hints for clusters.">Plan for clusters</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="rzaigmanagetune.htm" title="Since potentially significant differences exist in your communications environment, you have the capability to adjust variables that affect cluster communications to best match your environment.">Tune cluster performance</a></div>
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</div>
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</div>
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</body>
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