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https://issues.apache.org/jira/browse/HDFS-7291?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14184743#comment-14184743
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Haohui Mai commented on HDFS-7291:
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Why this needs to be done through native code? {{FileChannel#transferTo}}
should do the job.
> Persist in-memory replicas using unbuffered IO should only applies to
> supported Linux version
> ---------------------------------------------------------------------------------------------
>
> Key: HDFS-7291
> URL: https://issues.apache.org/jira/browse/HDFS-7291
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Affects Versions: 2.6.0
> Reporter: Xiaoyu Yao
> Assignee: Xiaoyu Yao
> Attachments: HDFS-7291.0.patch
>
>
> HDFS-7090 changes to persist in-memory replicas using unbuffered IO on Linux
> and Windows. On Linux distribution, it relies on the sendfile() API between
> two file descriptors to achieve unbuffered IO copy. According to Linux
> document at http://man7.org/linux/man-pages/man2/sendfile.2.html, this is
> only supported on Linux kernel 2.6.33+. This JIRA is to limit the usage of
> sendfile() for lazy persist only on Linux distribution with kernel version
> higher than 2.6.33. For unsupported version, lazy persist will fallback to
> normal buffered IO.
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