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https://issues.apache.org/jira/browse/MAPREDUCE-5065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13604815#comment-13604815
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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/12574096/MAPREDUCE-5065.branch-2.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+1 tests included{color}. The patch appears to include 1 new
or modified test files.
{color:red}-1 one of tests included doesn't have a timeout.{color}
{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/3424//testReport/
Console output:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3424//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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