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From "ac@hsk.hk" ...@hsk.hk>
Subject High Availability - second namenode (master2) issue: Incompatible namespaceIDs
Date Fri, 16 Nov 2012 04:28:47 GMT

Please help!

I have installed a Hadoop Cluster with a single master (master1) and have HBase running on
the HDFS.  Now I am setting up the second master  (master2) in order to form HA.  When I used
JPS to check the cluster, I found :

2782 Jps
2126 NameNode
2720 SecondaryNameNode
i.e. The datanode on this server could not be started

In the log file, found: 
2012-11-16 10:28:44,851 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.io.IOException:
Incompatible namespaceIDs in /app/hadoop/tmp/dfs/data: namenode namespaceID = 1356148070;
datanode namespaceID = 1151604993

One of the possible solutions to fix this issue is to:  stop the cluster, reformat the NameNode,
restart the cluster.
QUESTION: As I already have HBASE running on the cluster, if I reformat the NameNode, do I
need to reinstall the entire HBASE? I don't mind to have all data lost as I don't have many
data in HBASE and HDFS, however I don't want to re-install HBASE again.

On the other hand, I have tried another solution: stop the DataNode, edit the namespaceID
in current/VERSION (i.e. set namespaceID=1151604993), restart the datanode, it doesn't work:
Warning: $HADOOP_HOME is deprecated.
starting master2, logging to /usr/local/hadoop-1.0.4/libexec/../logs/hadoop-hduser-master2-master2.out
Exception in thread "main" java.lang.NoClassDefFoundError: master2
Caused by: java.lang.ClassNotFoundException: master2
	at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: master2.  Program will exit.
QUESTION: Any other solutions?



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