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https://issues.apache.org/jira/browse/MAPREDUCE-2257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13014085#comment-13014085
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Allen Wittenauer commented on MAPREDUCE-2257:
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>By default, distcp.copy.by.chunk is set to true in the configuration. The user
>can set it to >false to use the original distcp. But the type of destination
>will be checked afterward. >distcp.copy.by.chunk will remain true only if the
>destination file system is the distributed >file system.
This needs to get added to the release notes.
> distcp can copy blocks in parallel
> ----------------------------------
>
> Key: MAPREDUCE-2257
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2257
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: distcp
> Affects Versions: 0.21.0
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: MAPREDUCE-2257.patch
>
>
> The minimum unit of work for a distcp task is a file. We have files that are
> greater than 1 TB with a block size of 1 GB. If we use distcp to copy these
> files, the tasks either take a long long long time or finally fails. A better
> way for distcp would be to copy all the source blocks in parallel, and then
> stich the blocks back to files at the destination via the HDFS Concat API
> (HDFS-222)
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