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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2064) Warm HA NameNode going Hot
Date Tue, 02 Aug 2011 21:48:28 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2064?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13078455#comment-13078455

Konstantin Shvachko commented on HDFS-2064:

> 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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