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https://issues.apache.org/jira/browse/HDFS-2064?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13078455#comment-13078455
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Konstantin Shvachko commented on HDFS-2064:
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> If it starts much later than the NN, does it fetch both the fsimage file and
> the edits-log from the NN?
Yes it does. The patch that I attached has a SBN, which is an evolution BN. In
current implementation BN during registration with NN determines if it has an
old image and uploads the new one (along with edits). SBN will do the same
thing. No need to start as BN and then restart as SBN, as Dennis states.
Dennis, -importCheckpoint has a different purpose. If you have a separate image
directory, which is not the name or edits directory for your NN, you can import
data from the checkpoint directory and NN will save that state in its name
directories. The NN's name directories should be empty before you do
-importCheckpoint.
> Warm HA NameNode going Hot
> --------------------------
>
> Key: HDFS-2064
> URL: https://issues.apache.org/jira/browse/HDFS-2064
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: name-node
> Affects Versions: 0.22.0
> Reporter: Konstantin Shvachko
> Assignee: Konstantin Shvachko
> Priority: Blocker
> Attachments: WarmHA-GoingHot.pdf, failover-v-0.22.patch
>
>
> This is the design for automatic hot HA for HDFS NameNode. It involves use of
> HA software and LoadReplicator - external to Hadoop components, which
> substantially simplify the architecture by separating HA- from
> Hadoop-specific problems. Without the external components it provides warm
> standby with manual failover.
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