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From Uma Maheswara Rao G <mahesw...@huawei.com>
Subject RE: High Availability - second namenode (master2) issue: Incompatible namespaceIDs
Date Fri, 16 Nov 2012 07:56:15 GMT
If you format namenode, you need to cleanup storage directories of DataNode as well if that
is having some data already. DN also will have namespace ID saved and compared with NN namespaceID.
if you format NN, then namespaceID will be changed and DN may have still older namespaceID.
So, just cleaning the data in DN would be fine.



From: hadoop hive [hadoophive@gmail.com]
Sent: Friday, November 16, 2012 1:15 PM
To: user@hadoop.apache.org
Subject: Re: High Availability - second namenode (master2) issue: Incompatible namespaceIDs

Seems like you havn't format your cluster (if its 1st time made).

On Fri, Nov 16, 2012 at 9:58 AM, ac@hsk.hk<mailto:ac@hsk.hk> <ac@hsk.hk<mailto:ac@hsk.hk>>

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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