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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "PerformanceTuning" by RyanRawson
Date Wed, 17 Feb 2010 21:59:23 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

The "PerformanceTuning" page has been changed by RyanRawson.
http://wiki.apache.org/hadoop/PerformanceTuning?action=diff&rev1=8&rev2=9

--------------------------------------------------

   * Use a 64-bit platform, and a 64-bit JVM.
   * Your clients might need tuning: [[http://ryantwopointoh.blogspot.com/2009/01/performance-of-hbase-importing.html]]
   * Make sure that the command {{{java}}} implies {{{-server}}} on your machines, or else
you will have to explicitly enable it.
-  * Are you swapping?  JVMs hate swapping.  Adjusting [[http://www.sollers.ca/blog/2008/swappiness/|swappiness]]
may help.
+  * Are you swapping?  JVMs hate swapping.  Consider removing swap space.
   * By default, each regionserver puts up 10 listeners only.  Up it if you have measurable
traffic (See hbase.regionserver.handler.count in hbase-default.xml).
   * To speed up the inserts in a non critical job (like an import job), you can use Put.writeToWAL(false)
to bypass writing to the write ahead log.
   * New in HBase 0.21 (not released yet), you can set a table-scope attribute to defer the
write ahead log's flushes in order to improve write performance, this is now the default behavior.
Use HTableDescriptor.setDeferredLogFlush(false) when creating your table to instead make sure
every WAL edit is flushed to the Datanodes. The default setting of hbase.regionserver.optionallogflushinterval
is 1000 which means that in the worst case you lose 1 second of edits. Since the WAL is shared
on a region server for all regions, any other table not using this feature will flush your
other table's edits. 

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