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From "Rodrigo Schmidt (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-2257) distcp can copy blocks in parallel
Date Mon, 18 Apr 2011 08:08:06 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13020936#comment-13020936
] 

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

The class FileChunkPair is not really a pair, right? It stores 5 fields.

Can't we somehow unify the if/else in copy()? At least doCopyFile() could use doCopyFileChunks().

> 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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