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https://issues.apache.org/jira/browse/HDFS-4677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13661477#comment-13661477
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Hadoop QA commented on HDFS-4677:
---------------------------------
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12583750/HDFS-4677.2.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:red}-1 tests included{color}. The patch doesn't appear to include
any new or modified tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. The javadoc tool did not generate any
warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 1.3.9) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:red}-1 core tests{color}. The patch failed these unit tests in
hadoop-hdfs-project/hadoop-hdfs:
org.apache.hadoop.hdfs.server.blockmanagement.TestBlocksWithNotEnoughRacks
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-HDFS-Build/4414//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/4414//console
This message is automatically generated.
> Editlog should support synchronous writes
> -----------------------------------------
>
> Key: HDFS-4677
> URL: https://issues.apache.org/jira/browse/HDFS-4677
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 3.0.0, 1-win
> Reporter: Ivan Mitic
> Assignee: Ivan Mitic
> Attachments: HDFS-4677.2.patch, HDFS-4677.patch
>
>
> 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|http://msdn.microsoft.com/en-us/library/windows/desktop/aa364439(v=vs.85).aspx]
> while RandomAccessFile (“rws”) opens the file with the
> [FILE_FLAG_WRITE_THROUGH flag|http://support.microsoft.com/kb/99794].
> 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.
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