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https://issues.apache.org/jira/browse/HDFS-5453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13854395#comment-13854395
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Suresh Srinivas commented on HDFS-5453:
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>From my experience, I do not see many people wanting to move from commodity
>hardware. In fact extra dependencies for NFS storage, stonith power devices
>etc. have not gone well with many deployments. So lets agree do disagree.
Lets stick to the issue that jira is trying to solve. I know [~daryn] has been
trying to improve namenode performance for a large cluster. The problems that
he is addressing is relevant to some of the largest deployments of Hadoop. I
have not seen this issue for smaller clusters.
> Support fine grain locking in FSNamesystem
> ------------------------------------------
>
> Key: HDFS-5453
> URL: https://issues.apache.org/jira/browse/HDFS-5453
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: namenode
> Affects Versions: 2.0.0-alpha, 3.0.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
>
> The namesystem currently uses a course grain lock to control access. This
> prevents concurrent writers in different branches of the tree, and prevents
> readers from accessing branches that writers aren't using.
> Features that introduce latency to namesystem operations, such as cold
> storage of inodes, will need fine grain locking to avoid degrading the entire
> namesystem's throughput.
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