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https://issues.apache.org/jira/browse/HDFS-839?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12803147#action_12803147
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Wang Xu commented on HDFS-839:
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Konstantin: I think the difference between manual or automatic fail-over is not
only the operating procedure, but also the information consistency. Actually,
if we have an interface for the administrator to change BN/NN's role and a
monitor method, #1 could be automatically done with some external facilitate
such as HA software. However, the infomation which BN has decides the latency
of fail-over.
Thus, should we also decide which information BN should have for different HA
requirement? Such as:
# Persistent data: Namespace information, which has been logged by Backup Node,
with an administrative issue, BN could swith its Role to NN
# Run-time file status information: lease information, which could help the
service continueous during NN switch.
# Block distribution and replication information: which could accelerate the
fail-over procedure.
The different priority of data should have different synchronization policy,
and if we forward less significant information, it could avoid lock holding.
> The NameNode should forward block reports to BackupNode
> -------------------------------------------------------
>
> Key: HDFS-839
> URL: https://issues.apache.org/jira/browse/HDFS-839
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: name-node
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
>
> The BackupNode (via HADOOP-4539) receives a stream of transactions from
> NameNode. However, the BackupNode does not have block locations of blocks. It
> would be nice if the NameNode can forward all block reports (that it receives
> from DataNodes) to the BackupNode.
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