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From: Apache Wiki <wikidiffs@apache.org>
To: core-commits@hadoop.apache.org
Date: Thu, 30 Jul 2009 20:47:36 -0000
Message-ID: <20090730204736.23186.98708@eos.apache.org>
Subject: [Hadoop Wiki] Trivial Update of "Hbase/Troubleshooting" by stack

Dear Wiki user,

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The following page has been changed by stack:
http://wiki.apache.org/hadoop/Hbase/Troubleshooting

The comment on the change is:
Update

------------------------------------------------------------------------------
  === Causes ===
   * Slow datanodes are marked as down by DFSClient; eventually all replicas are marked as 'bad' (HADOOP-3831).
  === Resolution ===
+  * Apply HADOOP-4681 to your cluster or at least to the hadoop jar used by hbase.
   * Try setting '''dfs.datanode.socket.write.timeout''' to zero (in hadoop 0.18.x -- See HADOOP-3831 for detail and why not needed in hadoop 0.19.x).  See the thread at [http://mail-archives.apache.org/mod_mbox/hadoop-hbase-user/200810.mbox/%3C20126171.post@talk.nabble.com%3E message from jean-adrien] for some background.  Note, this is an hdfs client configuration so needs to be available in $HBASE_HOME/conf.  Making the change only in $HADOOP_HOME/conf is not sufficient.  Copy your amended hadoop-site.xml to the hbase conf directory or add this configuration to $HBASE_HOME/conf/hbase-site.xml.
   * Try increasing '''dfs.datanode.handler.count''' from its default of 3. This is a server configuration change so must be made in $HADOOP_HOME/conf/hadoop-site.xml. Try increasing it to 10, then by additional increments of 10. It probably does not make sense to use a value larger than the total number of nodes in the cluster. 
  
@@ -129, +130 @@

   * In accordance with your hardware, tune your heap space / garbage collector settings in the HBASE_OPTS variable of {{{$HBASE_CONF/hbase-env.sh}}}. Try the ''concurrent garbage collector'' {{{(-XX:+UseConcMarkSweepGC)}}} to avoid to stop the threads during GC. Read these articles for more info about Hotspot GC settings
      * [http://java.sun.com/docs/hotspot/gc1.4.2/faq.html Garbage collector FAQ] Quick overview
      * [http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html Tuning garbage collector in Java SE 6]
-  * For Java SE 6, some users have had success with {{{ -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:ParallelGCThreads=8 }}}
+  * For Java SE 6, some users have had success with {{{ -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:ParallelGCThreads=8 }}}.
+  * See HBase [wiki:PerformanceTuning Performance Tuning] for more on JVM GC tuning.
  
  [[Anchor(8)]]
  == 8. Problem: Instability on Amazon EC2 ==
@@ -158, +160 @@

      <value>60000</value>
    </property>
  }}}
-  * For Java SE 6, some users have had success with {{{ -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:ParallelGCThreads=8 }}}
+  * For Java SE 6, some users have had success with {{{ -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:ParallelGCThreads=8 }}}.  See HBase [wiki:PerformanceTuning Performance Tuning] for more on JVM GC tuning.
  
  [[Anchor(10)]]
  == 10. Problem: Scanners keep getting timeouts ==