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https://issues.apache.org/jira/browse/HADOOP-2065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12575164#action_12575164
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lohit vijayarenu commented on HADOOP-2065:
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Talked to Raghu regarding this.
bq For (2), it'll be nice if the namenode can delete the corrupted block if
there's a good replica on other nodes.
Right now, if there are good replicas, then namenode does replicate the good
blocks after it times out while trying to replicate corrupt block. This was
fixed by HADOOP-2012 , but if all replicas were corrupt, then namenodes keeps
on trying. It was decided that, this is desired behavior because one should
find out such corruptions.
bq For (3), I prefer if the namenode can still replicate the block.
bq 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.
With the current policy, if all blocks are corrupted, namenode would delete 2
of them and since it fails to replicate, it keep on trying as mentioned in
HADOOP-2012
Now, do we want that single replica to be replicated? In that case it is
similar to namenode not looping while replicating.
> Replication policy for corrupted block
> ---------------------------------------
>
> Key: HADOOP-2065
> URL: https://issues.apache.org/jira/browse/HADOOP-2065
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.14.1
> Reporter: Koji Noguchi
> Assignee: lohit vijayarenu
> Fix For: 0.17.0
>
>
> 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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