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https://issues.apache.org/jira/browse/HDFS-3743?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Masatake Iwasaki updated HDFS-3743:
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Assignee: (was: Masatake Iwasaki)
> QJM: improve formatting behavior for JNs
> ----------------------------------------
>
> Key: HDFS-3743
> URL: https://issues.apache.org/jira/browse/HDFS-3743
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Affects Versions: QuorumJournalManager (HDFS-3077)
> Reporter: Todd Lipcon
>
> Currently, the JournalNodes automatically format themselves when a new writer
> takes over, if they don't have any data for that namespace. However, this has
> a few problems:
> 1) if the administrator accidentally points a new NN at the wrong quorum (eg
> corresponding to another cluster), it will auto-format a directory on those
> nodes. This doesn't cause any data loss, but would be better to bail out with
> an error indicating that they need to be formatted.
> 2) if a journal node crashes and needs to be reformatted, it should be able
> to re-join the cluster and start storing new segments without having to fail
> over to a new NN.
> 3) if 2/3 JNs get accidentally reformatted (eg the mount point becomes
> undone), and the user starts the NN, it should fail to start, because it may
> end up missing edits. If it auto-formats in this case, the user might have
> silent "rollback" of the most recent edits.
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