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https://issues.apache.org/jira/browse/HDFS-2936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13277097#comment-13277097
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Eli Collins commented on HDFS-2936:
-----------------------------------
Why not just check the replication level at file creation/setrep and fail if
it's lower than the new configured value? No BlockManager changes etc. This
would require the user setrep all existing files to the new minimum replication
level when they set it, but that seems acceptable.
> Provide a better way to specify a HDFS-wide minimum replication requirement
> ---------------------------------------------------------------------------
>
> Key: HDFS-2936
> URL: https://issues.apache.org/jira/browse/HDFS-2936
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: name-node
> Affects Versions: 0.23.0
> Reporter: Harsh J
> Assignee: Harsh J
> Attachments: HDFS-2936.patch
>
>
> Currently, if an admin would like to enforce a replication factor for all
> files on his HDFS, he does not have a way. He may arguably set
> dfs.replication.min but that is a very hard guarantee and if the pipeline
> can't afford that number for some reason/failure, the close() does not
> succeed on the file being written and leads to several issues.
> After discussing with Todd, we feel it would make sense to introduce a second
> config (which is ${dfs.replication.min} by default) which would act as a
> minimum specified replication for files. This is different than
> dfs.replication.min which also ensures that many replicas are recorded before
> completeFile() returns... perhaps something like ${dfs.replication.min.user}.
> We can leave dfs.replication.min alone for hard-guarantees and add
> ${dfs.replication.min.for.block.completion} which could be left at 1 even if
> dfs.replication.min is >1, and let files complete normally but not be of a
> low replication factor (so can be monitored and accounted-for later).
> I'm prefering the second option myself. Will post a patch with tests soon.
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