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  1. Hadoop HDFS
  2. HDFS-4677

Editlog should support synchronous writes

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 1-win, 3.0.0-alpha1
    • Fix Version/s: 1-win, 2.1.0-beta
    • Component/s: None
    • Labels:
      None
    • Target Version/s:
    • Hadoop Flags:
      Reviewed

      Description

      In the current implementation, NameNode editlog performs syncs to the persistent storage using the FileChannel#force Java APIs. This API is documented to be slower compared to an alternative where RandomAccessFile is opened with "rws" flags (synchronous writes).

      We instrumented FileChannel#force on Windows and it some software/hardware configurations it can perform significantly slower than the “rws” alternative.

      In terms of the Windows APIs, FileChannel#force internally calls FlushFileBuffers while RandomAccessFile (“rws”) opens the file with the FILE_FLAG_WRITE_THROUGH flag.

      With this Jira I'd like to introduce a flag that provide means to configure NameNode to use synchronous writes. There is a catch though, the behavior of the "rws" flags is platform and hardware specific and might not provide the same level of guarantees as FileChannel#force w.r.t. flushing the on-disk cache. This is an expert level setting, and it should be documented as such.

        Attachments

        1. HDFS-4677.patch
          4 kB
          Ivan Mitic
        2. HDFS-4677.2.patch
          8 kB
          Ivan Mitic
        3. HDFS-4677.3.patch
          30 kB
          Chris Nauroth
        4. HDFS-4677.branch-1-win.patch
          4 kB
          Ivan Mitic
        5. HDFS-4677.3.patch
          30 kB
          Ivan Mitic
        6. HDFS-4677.branch-1-win.2.patch
          4 kB
          Ivan Mitic

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              • Assignee:
                ivanmi Ivan Mitic
                Reporter:
                ivanmi Ivan Mitic
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                Dates

                • Created:
                  Updated:
                  Resolved: