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Date: Mon, 14 Dec 2015 19:42:46 +0000 (UTC)
From: "Yongjun Zhang (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
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Subject: [jira] [Created] (MAPREDUCE-6572) Improved incremental data copy of
 distcp for truncated file
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Yongjun Zhang created MAPREDUCE-6572:
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             Summary: 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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