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https://issues.apache.org/jira/browse/HDFS-3092?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13259394#comment-13259394
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dhruba borthakur commented on HDFS-3092:
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I am trying to digest the meat of this approach, but one question that I do not
have an answer for: is it possible for the journal daemon to write data to
disks and nodes that do not share load from other non-journal writers? I feel
this requirement will be critical to ensure low variance of write latencies for
the journal. My experience is that a 5% increase in the latency of writes to
the transaction log causes a 20% degradation of namenode throughput in a large
cluster.
> Enable journal protocol based editlog streaming for standby namenode
> --------------------------------------------------------------------
>
> Key: HDFS-3092
> URL: https://issues.apache.org/jira/browse/HDFS-3092
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: ha, name-node
> Affects Versions: 0.24.0, 0.23.3
> Reporter: Suresh Srinivas
> Assignee: Suresh Srinivas
> Attachments: ComparisonofApproachesforHAJournals.pdf,
> MultipleSharedJournals.pdf, MultipleSharedJournals.pdf,
> MultipleSharedJournals.pdf
>
>
> Currently standby namenode relies on reading shared editlogs to stay current
> with the active namenode, for namespace changes. BackupNode used streaming
> edits from active namenode for doing the same. This jira is to explore using
> journal protocol based editlog streams for the standby namenode. A daemon in
> standby will get the editlogs from the active and write it to local edits. To
> begin with, the existing standby mechanism of reading from a file, will
> continue to be used, instead of from shared edits, from the local edits.
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