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https://issues.apache.org/jira/browse/HADOOP-659?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hairong Kuang reassigned HADOOP-659:
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Assignee: Hairong Kuang (was: Konstantin Shvachko)
> Boost the priority of re-replicating blocks that are far from their
> replication target
> --------------------------------------------------------------------------------------
>
> Key: HADOOP-659
> URL: https://issues.apache.org/jira/browse/HADOOP-659
> Project: Hadoop
> Issue Type: Improvement
> Components: dfs
> Affects Versions: 0.7.2
> Reporter: Konstantin Shvachko
> Assigned To: Hairong Kuang
>
> I see two types of replications that should be accelerated compared to all
> others.
> 1. Blocks that have only one remaining copy (but are required to have higher
> replication).
> 2. Blocks that have less than 1/3 of their replicas in place.
> The latter occurs when map/reduce sets replication of certain files to 10,
> and we want
> it happen fast to achieve better performance on the tasks.
> So I think we should distinguish two major groups of under-replicated blocks:
> first-priority (having only 1 copy or less than 1/3 of required replicas),
> and the rest.
> The name-node places first-priority blocks into the beginning of the
> neededReplication
> list, and the rest are placed at the end. That way the first-priority blocks
> will be replicated
> first and then the others.
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