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https://issues.apache.org/jira/browse/HADOOP-1845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12525546
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Raghu Angadi commented on HADOOP-1845:
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Assuming default replication is 3, setting mapred.submit.replication to 2
should not result in this exception. Relevant log from namenode from original
poster would be helpful.
The problem that Hairong described hasn't cause real failures yet as far as I
know. It only slows down increasing replication.. not sure by how much.
> Datanodes get error message "is valid, and cannot be written to"
> -----------------------------------------------------------------
>
> Key: HADOOP-1845
> URL: https://issues.apache.org/jira/browse/HADOOP-1845
> Project: Hadoop
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.14.1
> Reporter: Hairong Kuang
> Fix For: 0.15.0
>
>
> >> Copy from dev list:
> Our cluster has 4 nodes and i set the mapred.subimt.replication parameter to
> 2 on all nodes and the master. Everything has been restarted.
> Unfortuantely, we still have the same exception :
> 2007-09-05 17:01:59,623 ERROR org.apache.hadoop.dfs.DataNode:
> DataXceiver: java.io.IOException: Block blk_-5969983648201186681 is valid,
> and cannot be written to.
> at org.apache.hadoop.dfs.FSDataset.writeToBlock(FSDataset.java:515)
> at
> org.apache.hadoop.dfs.DataNode$DataXceiver.writeBlock(DataNode.java:822)
> at org.apache.hadoop.dfs.DataNode$DataXceiver.run(DataNode.java:727)
> at java.lang.Thread.run(Thread.java:595)
> >> end of copy
> The message shows that the namenode schedules to replicate a block to a
> datanode that already holds the block. The namenode block placement algorithm
> makes sure that it does not schedule a block to a datanode that is confirmed
> to hold a replica of the block. But it is not aware of any in-transit block
> placements (i.e. the scheduled but not confirmed block placements), so
> occasionally we may still see "is valid, and cannot be written to" errors.
> A fix to the problem is to keep track of all in-transit block placements,
> and the block placement algorithm considers these to-be-confirmed replicas
> as well.
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