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https://issues.apache.org/jira/browse/HADOOP-11794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15935814#comment-15935814
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Omkar Aradhya K S commented on HADOOP-11794:
--------------------------------------------

Thanks for the clarification [~yzhangal].
About this ...
{quote}
About other file systems, I did not get to test various file systems with this 
patch (except for DistributedFileSystem), we could follow-up with new jira to 
relax the file system requirement, and add corresponding tests for the 
corresponding file system?
{quote}
Is there any reason *not* to use *FileSystem.concat* & 
*FileSystem.getFileBlockLocations* ?

> 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, 
> 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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