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From amitsingh <amitsi...@cse.iitb.ac.in>
Subject DFS replication and Error Recovery on failure
Date Fri, 26 Dec 2008 18:08:16 GMT
Hi,

some  queries,

1) If i set value of dfs.replication to 3 only in hadoop-site.xml of 
namenode(master) and
then restart the cluster will this take effect. or  i have to change 
hadoop-site.xml at all slaves ?

2)
What can be possible cause of following error at a datanode. ?
ERROR org.apache.hadoop.dfs.DataNode: java.io.IOException: Incompatible 
namespaceIDs in
 /mnt/hadoop28/HADOOP/hadoop-0.16.3/tmp/dir/hadoop-hadoop/dfs/data: 
namenode namespaceID = 1396640905; datanode namespaceID = 820259954

If my data node goes down due to above error, what should i do in 
following scenarios
1) i have some data on the currupted data node that i need to recover, 
how can i recover that data ?
2) If i dont care about the data, but i want the node back on the 
cluster, can i just delete the /mnt/hadoop28/HADOOP/hadoop-0.16.3/tmp 
and include the node back in the cluster?


Regards
Amit

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