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Date: Sun, 15 May 2011 01:14:48 +0000 (UTC)
From: "Rodrigo Schmidt (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
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Subject: [jira] [Commented] (MAPREDUCE-2257) distcp can copy blocks in
 parallel
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-2257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13033623#comment-13033623 ] 

Rodrigo Schmidt commented on MAPREDUCE-2257:
--------------------------------------------

+1
Patch looks good. Just make sure it passes the QA test. Hadoop QA doesn't seem to have picked up the latest version.

> 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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