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hbase-5764 adding turning off SpecEx in Config chapter recommendations 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1324730 13f79535-47bb-0310-9956-ffa450edef68
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Doug Meil 2012-04-11 12:20:22 +00:00
parent b7844d9dd0
commit 10f783bd56
2 changed files with 10 additions and 0 deletions
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2
src/docbkx/book.xml
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@ -1253,6 +1253,8 @@ if (!b) {
map-tasks which will double-write your data to HBase; this is probably
not what you want.
</para>
<para>See <xref linkend="spec.ex"/> for more information.
</para>
</section>
</chapter> <!-- mapreduce -->

8
src/docbkx/configuration.xml
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@ -1585,6 +1585,13 @@ of all regions.
<para>For more information about compactions and the compaction file selection process, see <xref linkend="compaction"/></para>
</section>
<section xml:id="spec.ex"><title>Speculative Execution</title>
<para>Speculative Execution of MapReduce tasks is on by default, and for HBase clusters it is generally advised to turn off
Speculative Execution at a system-level unless you need it for a specific case, where it can be configured per-job.
Set the properties <varname>mapred.map.tasks.speculative.execution</varname> and
<varname>mapred.reduce.tasks.speculative.execution</varname> to false.
</para>
</section>
</section>
<section xml:id="other_configuration"><title>Other Configurations</title>
@ -1602,6 +1609,7 @@ of all regions.
on the size you need by surveying regionserver UIs; you'll see index block size accounted near the
top of the webpage).</para>
</section>
</section>
</section> <!-- important config -->