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From Andrew Wharton <andrew.whar...@nokia.com>
Subject Re: State of HA
Date Fri, 19 Jun 2009 18:39:42 GMT
Does anybody know the state of the Backupnamenode scheme that is
referenced here? I am looking for a Jira ticket that might give me some
more insight into the timeline for release. The hadoop-general email
list doesn't seem to have any information about this issue, which is
kind of worrying...

TIA.

-- Andrew

On Tue, 2009-06-02 at 16:57 +0200, ext Jean-Daniel Cryans wrote:
> Andrew,
> 
> I think you are confusing some components of the whole stack here. The
> Namenode is the master for HDFS just like the HMaster is the master
> for HBase. Hadoop is 2 things : HDFS and an implementation of
> MapReduce which also has a master, the JobTracker. HBase sits on all
> that.
> 
> So with regards with what's fixed, the HMaster SPOF is fixed for 0.20.
> The Namenode in 0.20 is still a SPOF. That means, if you want HA, you
> should get a really reliable machine for the Namenode but you can put
> the HMaster on any nodes you want.
> AFAIK, there is a BackupNamenode in Hadoop 0.21 that serves as a
> Namenode failover.



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