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https://issues.apache.org/jira/browse/HDFS-6482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14081603#comment-14081603
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James Thomas commented on HDFS-6482:
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[~sureshms] Is the documentation the Rollback section at
http://hadoop.apache.org/docs/r2.4.0/hadoop-project-dist/hadoop-hdfs/HdfsRollingUpgrade.html
correct? You are supposed to restart the DNs normally, without flags like
"-rollback" or "-rollingupgrade rollback"? If you restart the DNs with
"-rollback", everything should work normally and the previous directory should
be restored with the old layout. [~arpitagarwal], any thoughts on this?
> 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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