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https://issues.apache.org/jira/browse/HADOOP-1497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12505419
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Konstantin Shvachko commented on HADOOP-1497:
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See HADOOP-158

> Possibility of duplicate blockids if dead-datanodes come back up after 
> corresponding files were deleted
> -------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-1497
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1497
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>
> Suppose a datanode D has a block B that belongs to file F. Suppose the 
> datanode D dies and the namenode replicates those blocks to other datanodes. 
> No, suppose the user deletes file F. The namenode removes all the blocks that 
> belonged to file F. Now, suppose a new file F1 is created and the namenode 
> generates the same blockid B for this new file F1. 
> Suppose the old datanode D comes back to life. Now we have a valid corrupted 
> block B on datanode D.
> This case is possibly detected by the Client (using CRC). But does HDFS need 
> to handle this scenario better?

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