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HBASE-4092 performance.xml - adding batch-loading entry for using deferred log flush 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1151749 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack 2011-07-28 06:36:49 +00:00
parent aaad75743a
commit 22bb923beb
1 changed files with 15 additions and 1 deletions
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16
src/docbkx/performance.xml
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@ -199,7 +199,21 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
}</programlisting> }</programlisting>
</para> </para>
</section> </section>
</section> <section xml:id="def.log.flush">
<title>
Table Creation: Deferred Log Flush
</title>
<para>
The default behavior for Puts using the Write Ahead Log (WAL) is that <classname>HLog</classname> edits will be written immediately. If deferred log flush is used,
WAL edits are kept in memory until the flush period. The benefit is aggregated and asynchronous <classname>HLog</classname>- writes, but the potential downside is that if
the RegionServer goes down the yet-to-be-flushed edits are lost. This is safer, however, than not using WAL at all with Puts.
</para>
<para>
Deferred log flush can be configured on tables via <link
xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/HTableDescriptor.html">HTableDescriptor</link>. The default value of <varname>hbase.regionserver.optionallogflushinterval</varname> is 1000ms.
</para>
</section>
</section> <!-- batch loading -->
<section> <section>
<title>HBase Client</title> <title>HBase Client</title>