Hi Prabhu,

Did you clean the data dir on DataNodes? Whenever Namenode is formated the data directories of Datanodes needs to be cleaned up. As far as i remember it's the directory which you mention in dfs.data.dir in hdfs-site.xml file.You can do a google search for the error and you can get more details.
(Sorry, i dont have access to my cluster conf right now for telling you the exact property).

Thanks,
Anil

On Wed, Aug 8, 2012 at 12:49 AM, prabhu K <prabhu.hadoop@gmail.com> wrote:
Hi Users,
 
I have formatted hadoop cluster, formatted successfully. after stop &start hadoop, i hit the jps command in master, getting fine, but in slave machine am not getting data node, while see the data node log file, i am getting following error.
 
Data node(slave1):
2012-08-08 00:16:44,033 WARN org.apache.hadoop.hdfs.server.datanode.DataBlockScanner: Second Verification failed for blk_-3831635302961953167_1690. Exception : java.io.
IOException: Block blk_-3831635302961953167_1690 is not valid.
        at org.apache.hadoop.hdfs.server.datanode.FSDataset.getBlockFile(FSDataset.java:1072)
        at org.apache.hadoop.hdfs.server.datanode.FSDataset.getLength(FSDataset.java:1035)
        at org.apache.hadoop.hdfs.server.datanode.FSDataset.getVisibleLength(FSDataset.java:1045)
        at org.apache.hadoop.hdfs.server.datanode.BlockSender.<init>(BlockSender.java:94)
        at org.apache.hadoop.hdfs.server.datanode.BlockSender.<init>(BlockSender.java:81)
        at org.apache.hadoop.hdfs.server.datanode.DataBlockScanner.verifyBlock(DataBlockScanner.java:453)
        at org.apache.hadoop.hdfs.server.datanode.DataBlockScanner.verifyFirstBlock(DataBlockScanner.java:519)
        at org.apache.hadoop.hdfs.server.datanode.DataBlockScanner.run(DataBlockScanner.java:617)
        at java.lang.Thread.run(Thread.java:662)

data node(slave2)
2012-08-08 13:03:50,195 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.io.IOException: Incompatible namespaceIDs in /app/hadoop/tmp/dfs/data: namenode name
spaceID = 1434906924; datanode namespaceID = 474761520
        at org.apache.hadoop.hdfs.server.datanode.DataStorage.doTransition(DataStorage.java:232)
        at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:147)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:385)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:299)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1582)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1521)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1539)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:1665)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1682)
 
Please help me on this issue.
 
Thanks,
Prabhu.



--
Thanks & Regards,
Anil Gupta