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https://issues.apache.org/jira/browse/TEZ-2442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15207668#comment-15207668
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Bikas Saha commented on TEZ-2442:
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Its important to keep in mind that for significant perf gains, final merge of
the output could be avoided. So the output would live as separate files. Would
be good for the design to allow for this improvement in the future. ie. allows
multiple final output files to be written. [~rajesh.balamohan]
> Support DFS based shuffle in addition to HTTP shuffle
> -----------------------------------------------------
>
> Key: TEZ-2442
> URL: https://issues.apache.org/jira/browse/TEZ-2442
> Project: Apache Tez
> Issue Type: Improvement
> Affects Versions: 0.5.3
> Reporter: Kannan Rajah
> Assignee: Kannan Rajah
> Attachments: HDFS_based_shuffle_v2.pdf, Tez Shuffle using DFS.pdf,
> hdfs_broadcast_hack.txt, tez_hdfs_shuffle.patch
>
>
> In Tez, Shuffle is a mechanism by which intermediate data can be shared
> between stages. Shuffle data is written to local disk and fetched from any
> remote node using HTTP. A DFS like MapR file system can support writing this
> shuffle data directly to its DFS using a notion of local volumes and retrieve
> it using HDFS API from remote node. The current Shuffle implementation
> assumes local data can only be managed by LocalFileSystem. So it uses
> RawLocalFileSystem and LocalDirAllocator. If we can remove this assumption
> and introduce an abstraction to manage local disks, then we can reuse most of
> the shuffle logic (store, sort) and inject a HDFS API based retrieval instead
> of HTTP.
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