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From "Yongjun Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11794) distcp can copy blocks in parallel
Date Wed, 08 Feb 2017 05:45:42 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15857449#comment-15857449
] 

Yongjun Zhang commented on HADOOP-11794:
----------------------------------------

Rev 007:

1. Better -update handling, only copy files that need to be updated
2. Better error handling: if user enable ignore error, then continue after error
3. Do sanity checking in CopyCommitter, to ensure the chunk files are continuous for a given
file
4. Corrected implementation of file comparison in unit test, to handle variable size blocks
in a file.
5. Added some additional unit tests.

Thanks.


> 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,
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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