94 lines
7.2 KiB
HTML
94 lines
7.2 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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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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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Cluster resource group" />
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<meta name="abstract" content="A cluster resource group (CRG) is an i5/OS system object that is a set or grouping of cluster resources that are used to manage events that occur in a clustered environment. The cluster resource group describes a recovery domain and supplies the name of the cluster resource group exit program which gets called when certain cluster events occur." />
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<meta name="description" content="A cluster resource group (CRG) is an i5/OS system object that is a set or grouping of cluster resources that are used to manage events that occur in a clustered environment. The cluster resource group describes a recovery domain and supplies the name of the cluster resource group exit program which gets called when certain cluster events occur." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<title>Cluster resource group</title>
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</head>
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<body id="rzaigconceptscrg"><a name="rzaigconceptscrg"><!-- --></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">Cluster resource group</h1>
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<div><p><span><img src="./delta.gif" alt="Start of change" />A <dfn class="term">cluster resource group (CRG)</dfn> is
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an <span class="keyword">i5/OS™</span> system object
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that is a set or grouping of cluster resources that are used to manage events
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that occur in a clustered environment. The cluster resource group describes
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a recovery domain and supplies the name of the cluster resource group exit
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program which gets called when certain cluster events occur.<img src="./deltaend.gif" alt="End of change" /></span></p>
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<p><img src="./delta.gif" alt="Start of change" /> Clusters provides two choices in defining the relationships
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between nodes within a cluster: primary-backup model and peer model. Each
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of these models can be used together or separately depending on the needs
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of your environment.<img src="./deltaend.gif" alt="End of change" /></p>
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<div class="section"><h4 class="sectiontitle">Primary-backup model</h4><p><img src="./delta.gif" alt="Start of change" />All cluster
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resource groups of this category define nodes in the recovery domain with
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specific roles: either primary, backup or replicate. The primary and backup
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nodes are available access points for cluster resources. However only one
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node will be the active access point at a given point in time. This will be
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the primary node. Replicate nodes are not available to be an access point.
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This can be changed by assigning the replicate node a role of backup. Primary-backup
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model cluster resource groups are defined as data resilient, application resilient,
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or device resilient. Data resiliency enables multiple copies of data to be
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maintained on more than one node in a cluster and enables the point of access
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to be changed to a backup node. Application resiliency enables an application
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program to be restarted on either the same node or a different node in the
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cluster. Device resiliency enables a device resource to be moved (switched)
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to a backup node.<img src="./deltaend.gif" alt="End of change" /></p>
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<p>Each data and application cluster resource group has
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a cluster resource group exit program associated with it. The exit program
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is optional for resilient device cluster resource groups.</p>
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<p>In iSeries™ Navigator,
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cluster resource groups are referred to differently.</p>
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<ul><li><img src="./delta.gif" alt="Start of change" />A device CRG is referred to as a <span class="uicontrol">switchable
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device</span>.<img src="./deltaend.gif" alt="End of change" /></li>
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<li><img src="./delta.gif" alt="Start of change" />An application CRG is referred to as a <span class="uicontrol">switchable
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application</span>.<img src="./deltaend.gif" alt="End of change" /></li>
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<li><img src="./delta.gif" alt="Start of change" />A data CRG is referred to as a <span class="uicontrol">switchable data
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group</span>.<img src="./deltaend.gif" alt="End of change" /></li>
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</ul>
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</div>
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<div class="section"><h4 class="sectiontitle">Peer model</h4><p><img src="./delta.gif" alt="Start of change" />All cluster resource groups
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of this category define nodes in the recovery domain with a role of peer or
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replicate. The peer nodes are available to be the access point for the cluster
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resource group. All nodes defined as peer will be the access point when the
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cluster resource group is started. Replicate nodes are not available to be
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an access point. This can be changed by assigning the replicate node a role
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of peer. Within a peer CRG, each node contains replicated data that exists
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on each of the nodes. When a node fails in a peer CRG, the failure point is
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communicated to other nodes in the cluster, and those nodes continue the operation
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from the point of failure. <img src="./deltaend.gif" alt="End of change" /></p>
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<p>A cluster administrative domain
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is represented by a peer CRG with a recovery domain made up of only peer nodes. </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="rzaigconceptselements.htm" title="An iSeries cluster is a collection of one or more systems or partitions that work together as a single system. Use this information to understand the elements and their relationship to each other.">The elements of a cluster</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="rzaigconceptsrecoverydomain.htm" title="A recovery domain is a subset of cluster nodes that are grouped together in a cluster resource group (CRG) for a common purpose such as performing a recovery action or synchronizing events.">Recovery domain</a></div>
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<div><a href="rzaigconceptsexitprograms.htm" title="A cluster resource group exit program is called after a cluster-related event for a CRG occurs.">Cluster resource group exit programs</a></div>
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</div>
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</div>
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</body>
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