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https://issues.apache.org/jira/browse/HADOOP-11794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15938826#comment-15938826
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Chris Douglas commented on HADOOP-11794:
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bq. Once the new patch with all above changes is checked in, we need to back 
port it to older versions of hadoop, which will be addressed by new JIRAs?

This is usually handled in the same ticket, and by cherry-picking the patch. 
Backporting doesn't usually warrant a new JIRA unless the implementation is 
significantly different.

bq. I am not sure why this API is marked deprecated, it seems a good convenient 
API to exist. Wonder if we should remove the deprecation?

If it was deprecated in 0.21, evidently we're not serious about removing it.

> distcp can copy blocks in parallel
> ----------------------------------
>
>                 Key: HADOOP-11794
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11794
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: tools/distcp
>    Affects Versions: 0.21.0
>            Reporter: dhruba borthakur
>            Assignee: Yongjun Zhang
>         Attachments: HADOOP-11794.001.patch, HADOOP-11794.002.patch, 
> HADOOP-11794.003.patch, HADOOP-11794.004.patch, HADOOP-11794.005.patch, 
> HADOOP-11794.006.patch, HADOOP-11794.007.patch, HADOOP-11794.008.patch, 
> HADOOP-11794.009.patch, HADOOP-11794.010.patch, 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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