Hi,

Hadoop 2.1.0 release [1] is mentioned to be stable. I suggest we use this
feature for SS future release.

In hadoop 2, a main feature that is introduced is federation. This is where
there can be multiple namenodes/namespaces per cluster.  A namenode here
means a active namenode, a passive namenode and a secondary namenode.  So
with this approach, if we dedicate one namenode/namespace per tenant we can
get the tenant isolation.

As per the discussion I had with Prabath A, and Dhanuka on friday, we had 2
questions,

1) Can there be multiple namespaces in a single namenode? is it
recommended?

2) Let's say I have a federated namespace/namenodes. There are two
namenodes A /namespace A1 and namenode B/namespace B1, and have 3
datanodes. Can someone from namespace A1,  access the datanode's data in
anyway belonging to namespace B1. If not how is it handled?

IMO this could be handled to some extend with the usage of kerberos in
HDFS. The delegation tokens could be of use in this case. However will need
to look into this more.

I have raised these questions on the HDFS mailing lists, but have not yet
got any response.

I am yet to try the Hadoop 2 aforementioned release. Will do a POC and
update.

[1] Hadoop 
2.1.0-beta<http://hadoop.apache.org/releases.html#23+September%2C+2013%3A+Release+2.1.1-beta+available>


Thanks and Regards
*,Shani Ranasinghe*
Software Engineer
WSO2 Inc.; http://wso2.com
lean.enterprise.middleware

mobile: +94 77 2273555
linked in: lk.linkedin.com/pub/shani-ranasinghe/34/111/ab
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