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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7455) Introduce HA Service Protocol Interface
Date Wed, 03 Aug 2011 21:57:29 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13079058#comment-13079058

Suresh Srinivas commented on HADOOP-7455:

I am not sure if you need an HA state called "Neutral". It is standby (backup node) in disconnected
state. It is still a standby in my opinion. It is just that until it catches up with the active,
it cannot become active. Becoming from standby to active means possible loss of data.

bq. In the doc attached for HDFS-1623, it says 'It is important that only the active NN responds
to the client'. It achieves the same, but has dependency on the fencing done to the shared
storage; when a non‐active NN tries to write to the fenced shared storage it will fail &
the response to client will indicate failure.
I am not sure where in doc you are referring to. Fencing is needed during network partition.
If not shared stored, you do not want clients/datanodes to be talking to different nodes which
each think is active.

This is not specific to Linux-HA. It would be good to get your input on this jira.

> Introduce HA Service Protocol Interface
> ---------------------------------------
>                 Key: HADOOP-7455
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7455
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: util
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>         Attachments: HADOOP-7455.1.patch, HADOOP-7455.2.patch, HADOOP-7455.3.patch, HADOOP-7455.4.patch,
> This jira introduces a protocol interface to be implemented by services that provide
HA functionality.

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