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https://issues.apache.org/jira/browse/HDFS-7291?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14186062#comment-14186062
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Xiaoyu Yao commented on HDFS-7291:
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Validated the V2 patch passed TestNativeIO, TestScrLazyPersistFiles and
TestLazyPersistFiles under Windows Server 2012, CentOS 5.8 (LKV: 2.6.18 without
sendfile support) and Ubuntu 14 (LKV: 3.13.0 with sendfile support).
> Persist in-memory replicas with appropriate unbuffered copy API on POSIX and
> Windows
> ------------------------------------------------------------------------------------
>
> 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-7291.1.patch, HDFS-7291.2.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+.
> As pointed by Haowei in the discussion below, FileChannel#transferTo already
> has support for native unbuffered IO on POSIX platform. On Windows, JDK 6/7/8
> has not implemented native unbuffered IO yet. We change to use
> FileChannel#transfer for POSIX and our own native wrapper of CopyFileEx on
> Windows for unbuffered copy.
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