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https://issues.apache.org/jira/browse/SPARK-1529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14491863#comment-14491863
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Patrick Wendell commented on SPARK-1529:
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Hey Kannan,
We originally considered doing something like you are proposing, where we would
change our filesystem interactions to all use a Hadoop FileSystem class and
then we'd use Hadoop's LocalFileSystem. However, there were two issues:
1. We used POSIX API's that are not present in Hadoop. For instance, we use
memory mapping in various places, FileChannel in the BlockObjectWriter, etc.
2. Using LocalFileSystem has a substantial performance overheads compared with
our current code. So we'd have to write our own implementation of a Local
filesystem.
For this reason, we decided that our current shuffle machinery was
fundamentally not usable for non-POSIX environments. So we decided that
instead, we'd let people customize shuffle behavior at a higher level and we
implemented the pluggable shuffle components. So you can create a shuffle
manager that is specifically optimized for a particular environment (e.g. MapR).
Did you consider implementing a MapR shuffle using that mechanism instead?
You'd have to operate at a higher level, where you reason about shuffle
records, etc. But you'd have a lot of flexibility to optimize within that.
> Support setting spark.local.dirs to a hadoop FileSystem
> --------------------------------------------------------
>
> Key: SPARK-1529
> URL: https://issues.apache.org/jira/browse/SPARK-1529
> Project: Spark
> Issue Type: Improvement
> Components: Spark Core
> Reporter: Patrick Wendell
> Assignee: Kannan Rajah
> Attachments: Spark Shuffle using HDFS.pdf
>
>
> In some environments, like with MapR, local volumes are accessed through the
> Hadoop filesystem interface. We should allow setting spark.local.dir to a
> Hadoop filesystem location.
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