HBASE-11752 Document blockcache prefetch option (Misty Stanley-Jones)
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@ -2139,12 +2139,14 @@ rs.close();
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<section xml:id="cache.configurations">
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<title>General Cache Configurations</title>
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<para>Apart from the cache implementaiton itself, you can set some general
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configuration options to control how the cache performs.
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See <link
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xlink:href="http://hbase.apache.org/devapidocs/org/apache/hadoop/hbase/io/hfile/CacheConfig.html" />.
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After setting any of these options, restart or rolling restart your cluster for the
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configuration to take effect. Check logs for errors or unexpected behavior.</para>
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<para>Apart from the cache implementation itself, you can set some general configuration
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options to control how the cache performs. See <link
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xlink:href="http://hbase.apache.org/devapidocs/org/apache/hadoop/hbase/io/hfile/CacheConfig.html"
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/>. After setting any of these options, restart or rolling restart your cluster for the
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configuration to take effect. Check logs for errors or unexpected behavior.</para>
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<para>See also <xref linkend="blockcache.prefetch"/>, which discusses a new option
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introduced in <link xlink:href="https://issues.apache.org/jira/browse/HBASE-9857"
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>HBASE-9857</link>.</para>
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</section>
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<section
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@ -219,6 +219,37 @@
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A memory setting for the RegionServer process.
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</para>
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</section>
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<section xml:id="blockcache.prefetch">
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<title>Prefetch Option for Blockcache</title>
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<para><link xlink:href="https://issues.apache.org/jira/browse/HBASE-9857">HBASE-9857</link>
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adds a new option to prefetch HFile contents when opening the blockcache, if a columnfamily
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or regionserver property is set. This option is available for HBase 0.98.3 and later. The
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purpose is to warm the blockcache as rapidly as possible after the cache is opened, using
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in-memory table data, and not counting the prefetching as cache misses. This is great for
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fast reads, but is not a good idea if the data to be preloaded will not fit into the
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blockcache. It is useful for tuning the IO impact of prefetching versus the time before all
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data blocks are in cache. </para>
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<para>To enable prefetching on a given column family, you can use HBase Shell or use the
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API.</para>
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<example>
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<title>Enable Prefetch Using HBase Shell</title>
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<screen>hbase> create 'MyTable', { NAME => 'myCF', PREFETCH_BLOCKS_ON_OPEN => 'true' }</screen>
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</example>
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<example>
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<title>Enable Prefetch Using the API</title>
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<programlisting language="java">
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// ...
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HTableDescriptor tableDesc = new HTableDescriptor("myTable");
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HColumnDescriptor cfDesc = new HColumnDescriptor("myCF");
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cfDesc.setPrefetchBlocksOnOpen(true);
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tableDesc.addFamily(cfDesc);
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// ...
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</programlisting>
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</example>
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<para>See the API documentation for <link
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xlink:href="https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/io/hfile/CacheConfig.html"
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>CacheConfig</link>.</para>
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</section>
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<section xml:id="perf.rs.memstore.size">
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<title><varname>hbase.regionserver.global.memstore.size</varname></title>
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<para>See <xref linkend="hbase.regionserver.global.memstore.size"/>.
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