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From Daniel Templeton <dan...@cloudera.com>
Subject Re: Multiple namenodes
Date Fri, 22 Jul 2016 19:58:12 GMT
On 7/22/16 12:23 PM, Kun Ren wrote:
> Thanks a lot for your reply, Daniel, very helpful.
> About (1) :  I will consider this way, thanks. Also beside multiple 
> clusters, are there any other options to do so? Thanks.

HDFS does not support two active NNs in a single cluster.  Each DN 
belongs to a single NN, so a federated cluster is really multiple 
clusters that are stitched together at the NNs.

> About (2), if I understand correctly, HDFS used the quorum journal 
> manager(QJM) for HA, and the client  still only communicates with the 
> active namenode, not both node, am I understanding right?

I might be confusing HDFS with YARN, but I thought the way the client 
found the active NN was by just trying them all until one responds.


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