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https://issues.apache.org/jira/browse/HADOOP-1300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12501293
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Koji Noguchi commented on HADOOP-1300:
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bq. The goal while deleting excess replicas should be to maximize the number of
unique racks on which replicas will remain.
If this is for fault tolerance,
is there any reasons to adopt different policies for allocation and deletion?
Is it because this event happens less often so we're willing to pay the extra
overhead?
> deletion of excess replicas does not take into account 'rack-locality'
> ----------------------------------------------------------------------
>
> Key: HADOOP-1300
> URL: https://issues.apache.org/jira/browse/HADOOP-1300
> Project: Hadoop
> Issue Type: Bug
> Components: dfs
> Reporter: Koji Noguchi
> Assignee: Hairong Kuang
>
> One rack went down today, resulting in one missing block/file.
> Looking at the log, this block was originally over-replicated.
> 3 replicas on one rack and 1 replica on another.
> Namenode decided to delete the latter, leaving 3 replicas on the same rack.
> It'll be nice if the deletion is also rack-aware.
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