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https://issues.apache.org/jira/browse/HDFS-8966?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14729433#comment-14729433
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Daryn Sharp commented on HDFS-8966:
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Would you please elaborate on the design vision for doing the final separation?
In my rare spare cycles I've been trying to do the same thing.
> Separate the lock used in namespace and block management layer
> --------------------------------------------------------------
>
> Key: HDFS-8966
> URL: https://issues.apache.org/jira/browse/HDFS-8966
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Haohui Mai
> Assignee: Haohui Mai
>
> Currently the namespace and the block management layer share one giant lock.
> One consequence that we have seen more and more often is that the namespace
> hangs due to excessive activities from the block management layer. For
> example, the NN might take a couple hundred milliseconds to handle a large
> block report. Because the NN holds the write lock during processing the block
> report, all namespace requests are paused. In production we have seen these
> lock contentions cause long latencies and instabilities in the cluster.
> This umbrella jira proposes to separate the lock used by namespace and the
> block management layer.
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