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https://issues.apache.org/jira/browse/HDFS-2141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13069869#comment-13069869
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Konstantin Shvachko commented on HDFS-2141:
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> Looks like you have BN and SBN and perhaps ABN when the SBN turns active.
In my terminology there is only one NameNode. And it can have different roles
ACTIVE, BACKUP, STANDBY.
>You seem to suggest that backup NN is the only way to be in standby mode
I do not suggest that. Both 2a and 2b are valid for NN in standby mode (or role
as we used to call it).
> Checkpointer is not NN mode or even a Namenode.
Why not? It is a very rudimentary NN that can read image and edits, temporary
create the namespace structure in RAM same as on NN, and then write it back to
disk.
> I also like the notion that a NN runs a set of services depending on the
> "mode".
I like that too. So the NN in standby mode will run a journal digestion
service, may run checkpoint service, but will not run lease recovery or block
replication services. And NN in active mode is not allowed to run the
checkpoint service.
Can we keep the word "role" for that?
> Remove NameNode roles Active and Standby (they become states)
> -------------------------------------------------------------
>
> Key: HDFS-2141
> URL: https://issues.apache.org/jira/browse/HDFS-2141
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: name-node
> Reporter: Suresh Srinivas
> Assignee: Suresh Srinivas
> Fix For: 0.23.0
>
> Attachments: HDFS-2141.1.patch, HDFS-2141.patch
>
>
> In HDFS, following roles are supported in NameNodeRole: ACTIVE, BACKUP,
> CHECKPOINT and STANDBY.
> Active and Standby are the state of the NameNode. While Backup and CheckPoint
> are the name/role of the daemons that are started. This mixes up the run time
> state of NameNode with the daemon role. I propose changing the NameNodeRole
> to: NAMENODE, BACKUP, CHECKPOINT. HDFS-1974 will introduce the states active
> and standby to the daemon that is running in the role NAMENODE.
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