0cd5218f50
Closes-Bug: #1352053 Minor ormatting, capitalization and verb tense corrections Corrections to IP addresses in some examples and replacing "VIP" with "virtual IP" for simplicity. Calling out split-brain possibility in 2-node cluster with required quorum override Amended with feedback from Andreas Jaeger and Christian Berendt on patch set 1 and 2 Change-Id: I1cc532d73483ad82d1ceaec92a8caf11071a7d0e
55 lines
2.9 KiB
XML
55 lines
2.9 KiB
XML
<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0"
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xml:id="_set_basic_cluster_properties">
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<title>Set basic cluster properties</title>
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<para>Once your Pacemaker cluster is set up, it is recommended to set a few
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basic cluster properties. To do so, start the <literal>crm</literal> shell and change
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into the configuration menu by entering
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<literal>configure</literal>. Alternatively. you may jump straight into the Pacemaker
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configuration menu by typing <literal>crm configure</literal> directly from a shell
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prompt.</para>
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<para>Then, set the following properties:</para>
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<programlisting>property no-quorum-policy="ignore" \ # <co xml:id="CO2-1"/>
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pe-warn-series-max="1000" \ # <co xml:id="CO2-2"/>
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pe-input-series-max="1000" \
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pe-error-series-max="1000" \
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cluster-recheck-interval="5min" # <co xml:id="CO2-3"/></programlisting>
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<calloutlist>
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<callout arearefs="CO2-1">
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<para>
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Setting <literal>no-quorum-policy="ignore"</literal> is required in 2-node Pacemaker
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clusters for the following reason: if quorum enforcement is enabled,
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and one of the two nodes fails, then the remaining node can not
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establish a <emphasis>majority</emphasis> of quorum votes necessary to run services, and
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thus it is unable to take over any resources. In this case, the appropriate
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workaround is to ignore loss of quorum in the cluster. This should only <emphasis>only</emphasis> be done in 2-node clusters: do not set this property in
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Pacemaker clusters with more than two nodes. Note that a two-node cluster with this setting exposes a risk of split-brain because either half of the cluster, or both, are able to become active in the event that both nodes remain online but lose communication with one another. The preferred configuration is 3 or more nodes per cluster.
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</para>
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</callout>
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<callout arearefs="CO2-2">
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<para>
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Setting <literal>pe-warn-series-max</literal>, <literal>pe-input-series-max</literal> and
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<literal>pe-error-series-max</literal> to 1000 instructs Pacemaker to keep a longer
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history of the inputs processed, and errors and warnings generated, by
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its Policy Engine. This history is typically useful in case cluster
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troubleshooting becomes necessary.
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</para>
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</callout>
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<callout arearefs="CO2-3">
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<para>
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Pacemaker uses an event-driven approach to cluster state
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processing. However, certain Pacemaker actions occur at a configurable
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interval, <literal>cluster-recheck-interval</literal>, which defaults to 15 minutes. It
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is usually prudent to reduce this to a shorter interval, such as 5 or
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3 minutes.
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</para>
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</callout>
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</calloutlist>
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<para>Once you have made these changes, you may <literal>commit</literal> the updated
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configuration.</para>
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</section>
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