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From "Rajiv Chittajallu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2231) Configuration changes for HA namenode
Date Tue, 16 Aug 2011 01:00:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13085465#comment-13085465
] 

Rajiv Chittajallu commented on HDFS-2231:
-----------------------------------------

{quote}
Terminology:
   1. NNAddress1, NNAddress2 - address of individual NNs
   2. NNActiveAddress - Where the active provides namenode service.
   3. NNStandbyAddress - Where the standby namenode service such as read-only operations.
   4. NNVIPAddress/FailoverAddress - this is the VIP address used by HA setup. This address
is owned by the active namenode and NNActiveAddress is same as NNVIPAddress.
{quote}

>From the above description, I see only 2 IP's that could moved between nodes, NNActiveAddress
and NNStandbyAddress, and can be possibly called as vips. 

{quote}
HA solution uses VIP address:

    1. System needs to be configured with three sets of addresses, NNVIPAddress, NNAddress1
and NNAddress2.
    2. Clients and datanodes use NNVIPAddress as NNActiveAddress.
    3. To discover NNStandbyAddress clients and datanode may try NNAddress1 and NNAddress2
or use mechanism such as Zookeeper.
{quote}

And the discovery part is what probably confusing every one. As Allen said, this seem to be
unnecessary. If you can't rely on the VIP address, then the implementation is not correct.
Clients doesn't have to know the physical host address.

Using Zookeeper and IP failover are two different solutions to notify clients of the change
in the failover of the namenode.




> Configuration changes for HA namenode
> -------------------------------------
>
>                 Key: HDFS-2231
>                 URL: https://issues.apache.org/jira/browse/HDFS-2231
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>             Fix For: HA branch (HDFS-1623)
>
>
> This jira tracks the changes required for configuring HA setup for namenodes.

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