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https://issues.apache.org/jira/browse/HDFS-2141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13068662#comment-13068662
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Suresh Srinivas commented on HDFS-2141:
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> "The NameNode in HDFS, in addition to its primary role serving client 
> requests, can alternatively execute either of two other roles, either a 
> CheckpointNode or a BackupNode. The role is specified at the node startup..." 
> Go to Chapter 9.2.5.
First, this is before HA. Second, I do not parse role as strictly as you are.

> Can you live with roles, without renaming 2 of them into states? I think it 
> is an unnecessary change in terminology, which involved code change.
I prefer states, because these are truly states. I associate more permanent 
association of a process to a role, unlike state changes. As a product evolves, 
things change. It would be better to use the correct abstractions than try to 
keep a doc from getting outdated.

> 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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