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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2065) Replication policy for corrupted block
Date Tue, 16 Oct 2007 20:14:51 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12535332
] 

Raghu Angadi commented on HADOOP-2065:
--------------------------------------

#2 above will be handled in HADOOP-2012. When it detects a corrupt block, it just asks the
Namenode to delete it (same interface is used by client when it detects a bad block). In this
case, namenode deletes the block as long as there are more replicas. So it does not really
make sure that there is at least one _good_ replica.


> Replication policy for corrupted block 
> ---------------------------------------
>
>                 Key: HADOOP-2065
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2065
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.14.1
>            Reporter: Koji Noguchi
>
> Thanks to HADOOP-1955, even if one of the replica is corrupted, the block should get
replicated from a good replica relatively fast.
> Created this ticket to continue the discussion from http://issues.apache.org/jira/browse/HADOOP-1955#action_12531162.
> bq. 2. Delete corrupted source replica
> bq. 3. If all replicas are corrupt, stop replication.
> For (2), it'll be nice if the namenode can delete the corrupted block if there's a good
replica on other nodes.
> For (3), I prefer if the namenode can still replicate the block.
> Before 0.14, if the file was corrupted, users were still able to pull the data and decide
if they want to delete those files. (HADOOP-2063)
> In 0.14 and later, we cannot/don't replicate these blocks so they eventually get lost.
> To make the matters worse, if the corrupted file is accessed, all the corrupted replicas
would be deleted except for one and stay as replication factor of 1 forever.
>  

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