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From Harsh J <ha...@cloudera.com>
Subject Re: Question about HA and Federation
Date Thu, 20 Dec 2012 17:12:23 GMT
Hi ESGLinux,

Federation and HA are two distinct features that share some common
properties but nothing more. You can turn on HA for any selected
Namespace but it is not necessarily needed to be that all Namespaces
have HA.

Perhaps an example will clear it up for you.

I have a local instance that is configured to run several namespaces:
ns1, ns2, and ns3 (Federated Namespaces).
The namespace ns1 hosts my HBase tables and is critical to me, so I
have also turned on HA for this namespace alone.
The other two namespaces ns2 and ns3 are used only for regular query
jobs so its not yet very important for me to have HA on it. So I run
them without HA.

Thus I have 4 NameNode processes in my cluster in all, given my design
above: (2 NNs under ns1, in HA mode) + (1 NN of ns2) + (1 NN of ns3).

On Thu, Dec 20, 2012 at 10:00 PM, ESGLinux <esggrupos@gmail.com> wrote:
> Hi All,
> I´m going to test a hadoop cluster and I have a doubt about HA and
> Federation.
> With federation I Have a NameNode per namespace and with HA I have an Active
> NameNode and a standby NameNode.
> so, as I have sevaral namespaces, do I need an Active NameNode and a standby
> nameNode per namespace?
> I have read this documentation but It´s not clear for me :-(
> https://ccp.cloudera.com/display/CDH4DOC/Introduction+to+Hadoop+High+Availability
> http://hadoop.apache.org/docs/r0.23.0/hadoop-yarn/hadoop-yarn-site/Federation.html
> Thanks in advance
> ESGLinux

Harsh J

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