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https://issues.apache.org/jira/browse/MAPREDUCE-5065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13603437#comment-13603437
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Hadoop QA commented on MAPREDUCE-5065:
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{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12573882/MAPREDUCE-5065.branch-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:green}+1 core tests{color}. The patch passed unit tests in
hadoop-tools/hadoop-distcp.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3419//testReport/
Console output:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3419//console
This message is automatically generated.
> DistCp should skip checksum comparisons if block-sizes are different on
> source/target.
> --------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-5065
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5065
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: distcp
> Affects Versions: 2.0.3-alpha, 0.23.5
> Reporter: Mithun Radhakrishnan
> Assignee: Mithun Radhakrishnan
> Attachments: MAPREDUCE-5065.branch-0.23.patch,
> MAPREDUCE-5065.branch-2.patch
>
>
> When copying files between 2 clusters with different default block-sizes, one
> sees that the copy fails with a checksum-mismatch, even though the files have
> identical contents.
> The reason is that on HDFS, a file's checksum is unfortunately a function of
> the block-size of the file. So you could have 2 different files with
> identical contents (but different block-sizes) have different checksums.
> (Thus, it's also possible for DistCp to fail to copy files on the same
> file-system, if the source-file's block-size differs from HDFS default, and
> -pb isn't used.)
> I propose that we skip checksum comparisons under the following conditions:
> 1. -skipCrc is specified.
> 2. File-size is 0 (in which case the call to the checksum-servlet is moot).
> 3. source.getBlockSize() != target.getBlockSize(), since the checksums are
> guaranteed to differ in this case.
> I have a patch for #3.
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