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https://issues.apache.org/jira/browse/HDFS-6482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14069541#comment-14069541
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James Thomas commented on HDFS-6482:
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In response to [~cmccabe]'s comments:
One thread per storage directory doesn't make sense here since this is the
number of threads to use for the hard link process for ONE storage directory.
The hard link processes for the storage directories are currently not run in
parallel.
We can create a separate JIRA to add the native code to the regular hard link
path. I've created a separate code path in this change for the upgrade to the
block ID-based layout, and I want to focus on optimizing that in this JIRA.
[~sureshms], any thoughts?
> Use block ID-based block layout on datanodes
> --------------------------------------------
>
> Key: HDFS-6482
> URL: https://issues.apache.org/jira/browse/HDFS-6482
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 2.5.0
> Reporter: James Thomas
> Assignee: James Thomas
> Attachments: 6482-design.doc, HDFS-6482.1.patch, HDFS-6482.2.patch,
> HDFS-6482.3.patch, HDFS-6482.4.patch, HDFS-6482.5.patch, HDFS-6482.6.patch,
> HDFS-6482.7.patch, HDFS-6482.8.patch, HDFS-6482.9.patch, HDFS-6482.patch,
> hadoop-24-datanode-dir.tgz
>
>
> Right now blocks are placed into directories that are split into many
> subdirectories when capacity is reached. Instead we can use a block's ID to
> determine the path it should go in. This eliminates the need for the LDir
> data structure that facilitates the splitting of directories when they reach
> capacity as well as fields in ReplicaInfo that keep track of a replica's
> location.
> An extension of the work in HDFS-3290.
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