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https://issues.apache.org/jira/browse/MAPREDUCE-6572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15056577#comment-15056577
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Yongjun Zhang commented on MAPREDUCE-6572:
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This idea is based on in person discussion with John, and he will be taking a
further look, so I assigned to him. Thanks John.
> Improved incremental data copy of distcp for truncated file
> -----------------------------------------------------------
>
> Key: MAPREDUCE-6572
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6572
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Yongjun Zhang
> Assignee: John Zhuge
>
> MAPREDUCE-5899 improves distcp by supporting incremental data copy. That is,
> if a file is only appended since it was copied last time, only new data need
> to be copied.
> This improvement was done before HDFS truncate feature (HDFS-3107) was
> implemented. Since we support truncate, if a large file is truncated a little
> bit, the whole file will still need to be copied, even with the solution of
> MAPREDUCE-5899.
> Creating this jira to improve the situation, by possibly remembering the
> smallest truncated size, so there is chance to only append from that size on.
> Thanks.
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