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https://issues.apache.org/jira/browse/HDFS-6581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14106042#comment-14106042
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Todd Lipcon commented on HDFS-6581:
-----------------------------------
If you truncate() a file while a reader has it mmapped, will the reader get 0s
or a bus error? I seem to recall it's the latter, which may be a bit nasty for
a revocation path.
Why not do what we discussed a couple months back and have a disk replica with
mlock? I think this will prevent any writeback.
> Write to single replica in memory
> ---------------------------------
>
> Key: HDFS-6581
> URL: https://issues.apache.org/jira/browse/HDFS-6581
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Arpit Agarwal
> Assignee: Arpit Agarwal
> Attachments: HDFSWriteableReplicasInMemory.pdf
>
>
> Per discussion with the community on HDFS-5851, we will implement writing to
> a single replica in DN memory via DataTransferProtocol.
> This avoids some of the issues with short-circuit writes, which we can
> revisit at a later time.
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