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http://issues.apache.org/jira/browse/HADOOP-738?page=comments#action_12452613 ] 
            
eric baldeschwieler commented on HADOOP-738:
--------------------------------------------

Well the discussion does seem to be on the topic of the subject.  As discussed 
in the thread there are several reasons to consider the change.  Enhancing the 
description could be done.

I agree that we probably should fix the interaction of the CRC files in the 
current copy too.  Although renaming them so they are visible would help a lot 
no mater what.

I also agree that we will need sub-block CRC info even when we move the CRC 
data to be a block attribute.

Moving multi-terrabyte objects to local disk is not the prototypical use of 
Hadoop in our environment.  It is certainly not the prototypical reason we 
invoke -get or -copyToLocal.

We don't seem to be converging here.  Maybe we should create two commands.  One 
which is typically used for lightweight copies and does not write CRCs and one 
which does and has an inverse command that validates the CRCs on import.  
Although what happens when a CRC does not match on import?  The CRC exporter 
would create visible CRCs and would have well defined semantics for overwriting 
files.  (Failing if the target directory would avoid the problem in the 
description ...)

> dfs get or copyToLocal should not copy crc file
> -----------------------------------------------
>
>                 Key: HADOOP-738
>                 URL: http://issues.apache.org/jira/browse/HADOOP-738
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.8.0
>         Environment: all
>            Reporter: Milind Bhandarkar
>         Assigned To: Milind Bhandarkar
>             Fix For: 0.9.0
>
>         Attachments: hadoop-crc.patch
>
>
> Currently, when we -get or -copyToLocal a directory from DFS, all the files 
> including crc files are also copied. When we -put or -copyFromLocal again, 
> since the crc files already exist on DFS, this put fails. The solution is not 
> to copy checksum files when copying to local. Patch is forthcoming.

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