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https://issues.apache.org/jira/browse/HDFS-839?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12803086#action_12803086
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Konstantin Shvachko commented on HDFS-839:
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I agree with Eli that block report handling is just a sub-task of the general
design.
I am not sure the hot standby solution should be rushed to achieve in one
single step. Creating BackupNode I thought we would go through 3 stages:
# _Manual fail-over to BN_. You start a BacupNode and issue an admin command to
the name-node to switch to the BN. The name-node enters safe mode, and replies
to all data-nodes to their heartbeats that they should switch to BN. When the
name-node does not have any more live data-nodes, you can safely turn it off.
Similarly for active clients, NN asks them to connect to BN, when they do ls or
apply for lease extension. This is useful when you need to take NN down for a
scheduled service or hardware upgrade.
# _Automatic fail-over to BN._ This will be the warm standby.
Cluster components a priori know where to switch in case of failure. And if NN
fails they switch to BN. This has a wide range of possible solutions, and may
need a lot of work. With warm standby you still have down-time measured in tens
of minutes, but it is useful for both scheduled and unscheduled NN shutdowns.
# _Hot stand by._ This is a good thing to have. My intuition is that most
people will be well satisfied with the warm solution.
I was wondering is there any interest in doing (1)?
> 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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