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From Chris Nauroth <cnaur...@hortonworks.com>
Subject Re: Namenode HA and data loss
Date Tue, 13 Jan 2015 23:17:52 GMT
Yes, if this is an HDFS cluster deployed with HA using the Quorum Journal
Manager, then it is protected against data loss.  This documentation page
describes the configuration and how the architecture achieves it.

http://hadoop.apache.org/docs/r2.6.0/hadoop-project-dist/hadoop-hdfs/HDFSHighAvailabilityWithQJM.html

There can be a small risk of an HDFS client reading stale data from an old
NameNode that still thinks it's active.  To mitigate against this, you can
configure fencing methods to stop the old NameNode.  For more information
on this, see "dfs.ha.fencing.methods" in the same document.

Chris Nauroth
Hortonworks
http://hortonworks.com/


On Tue, Jan 13, 2015 at 2:46 PM, Kondala Palaka <
kpalaka@gurudatasolutions.com> wrote:

> Hi friends,
>
>
>
> Is there really *zero* data loss in case of a namenode failure in an HA
> (active-passive) environment?
>
>
>
> Thanks in advance for any pointers..
>
> *Kondala Palaka*
>
>
>

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