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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10971) Distcp should not copy replication factor if source file is erasure coded
Date Tue, 11 Oct 2016 20:20:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15566464#comment-15566464
] 

Andrew Wang commented on HDFS-10971:
------------------------------------

I thought we were going to copy S3's behavior, which shows replication as 1? It's more accurate
than "0", since there is in fact 1 replica, and seems less likely to break application expectations.

Instead of checking for a "0" or something, we should also add an API like {{isErasureCoded}}
to FileStatus. That's more future-proof than encoding special meaning into the replication
factor.

> Distcp should not copy replication factor if source file is erasure coded
> -------------------------------------------------------------------------
>
>                 Key: HDFS-10971
>                 URL: https://issues.apache.org/jira/browse/HDFS-10971
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: distcp
>    Affects Versions: 3.0.0-alpha1
>            Reporter: Wei-Chiu Chuang
>            Assignee: Wei-Chiu Chuang
>              Labels: hdfs-ec-3.0-must-do
>         Attachments: HDFS-10971.testcase.patch
>
>
> The current erasure coding implementation uses replication factor field to store erasure
coding policy.
> Distcp copies the source file's replication factor to the destination if {{-pr}} is specified.
However, if the source file is EC, the replication factor (which is EC policy) should not
be replicated to the destination file. When a HdfsFileStatus is converted to FileStatus, the
replication factor is set to 0 if it's an EC file.
> In fact, I will attach a test case that shows trying to replicate the replication factor
of an EC file results in an IOException: "Requested replication factor of 0 is less than the
required minimum of 1 for /tmp/dst/dest2"



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