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From Harsh J <ha...@cloudera.com>
Subject Re: question about ZKFC daemon
Date Thu, 27 Dec 2012 16:34:30 GMT

There are two different things here: Automatic Failover and Quorum
Journal Manager. The former, used via a ZooKeeper Failover Controller,
is to manage failovers automatically (based on health checks of NNs).
The latter, used via a set of Journal Nodes, is a medium of shared
storage for namesystem transactions that helps enable HA.

In a typical deployment, you want 3 or more (odd) JournalNodes for
reliable HA, preferably on nodes of their own if possible (like you
would for typical ZooKeepers, and you may co-locate with those as
well) and one ZKFC for each NameNode (connected to the same ZK

On Thu, Dec 27, 2012 at 5:33 PM, ESGLinux <esggrupos@gmail.com> wrote:
> Hi all,
> I have a doubt about how to deploy the Zookeeper in a NN HA  cluster,
> As far as I know, I need at least three nodes to run three ZooKeeper
> FailOver Controller (ZKFC). I plan to put these 3 daemons this way:
> - Active NameNode + 1 ZKFC daemon
> - Standby NameNode + 1 ZKFC daemon
> - JobTracker node + 1 ZKFC daemon, (is this right?)
> so the quorum is formed with these three nodes. The nodes that runs a
> namenode are right because the ZKFC monitors it, but what does the third
> daemon?
> as I read from this url:
> https://ccp.cloudera.com/display/CDH4DOC/Software+Configuration+for+Quorum-based+Storage#SoftwareConfigurationforQuorum-basedStorage-AutomaticFailoverConfiguration
> this daemons are only related with NameNodes, (Health monitoring - the ZKFC
> pings its local NameNode on a periodic basis with a health-check command.)
> so what does the third ZKFC? I used the jobtracker node but I could use
> another node without any daemon on it...
> Thanks in advance,
> ESGLInux,

Harsh J

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