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From "Yongjun Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-11794) distcp can copy blocks in parallel
Date Thu, 19 Jan 2017 23:57:27 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-11794?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Yongjun Zhang updated HADOOP-11794:
    Attachment: HADOOP-11794.001.patch

Sorry for the long delay, attaching patch rev 001. 

With this patch, we can pass -chunksize <x> to distcp,  to tell distcp to split large
files into chunks, each containing a number of blocks specified by this new parameter, except
the last chunk of a file may be smaller.  CopyMapper will treat each chunk as a single file
so the chunks can be copied in parallel; And the CopyCommitter concat the parts into one target

With this switch, we will enable preserving block size, disable the randomization of entries
in the sequence file, disable append feature.
We could do further optimization as follow-ups.

Any review is very welcome!

Thanks a lot.

> 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, 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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