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From amitsingh <amitsi...@cse.iitb.ac.in>
Subject DFS replication and Error Recovery on failure
Date Sat, 27 Dec 2008 07:36:49 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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