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      <a name="group-replication-deploying-instances">
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      20.2.1.1 Deploying Instances for Group Replication
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  <p>
   The first step is to deploy at least three instances of MySQL
        Server, this procedure demonstrates using multiple hosts for the
        instances, named s1, s2, and s3. It is assumed that MySQL Server
        is installed on each host (see
   <a class="xref" href="installing.html" title="Chapter 2 Installing MySQL">
    Chapter 2,
    <i>
     Installing MySQL
    </i>
   </a>
   ).
        The Group Replication plugin is provided with MySQL Server
        8.4; no additional software is required, although
        the plugin must be installed in the running MySQL server. See
   <a class="xref" href="group-replication-deploying-instances.html" title="20.2.1.1 Deploying Instances for Group Replication">
    Section 20.2.1.1, “Deploying Instances for Group Replication”
   </a>
   ; for
        additional information, see
   <a class="xref" href="server-plugins.html" title="7.6 MySQL Server Plugins">
    Section 7.6, “MySQL Server Plugins”
   </a>
   .
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  <p>
   In this example, three instances are used for the group, which
        is the minimum number of instances to create a group. Adding
        more instances increases the fault tolerance of the group. For
        example if the group consists of three members, in event of
        failure of one instance the group can continue. But in the event
        of another failure the group can no longer continue processing
        write transactions. By adding more instances, the number of
        servers which can fail while the group continues to process
        transactions also increases. The maximum number of instances
        which can be used in a group is nine. For more information see
   <a class="xref" href="group-replication-failure-detection.html" title="20.1.4.2 Failure Detection">
    Section 20.1.4.2, “Failure Detection”
   </a>
   .
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