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From Paul Baclace <paul.bacl...@gmail.com>
Subject EC2 cluster interconnection: fs.default.name= public versus private DNS
Date Wed, 14 Sep 2011 22:35:29 GMT
[I answer my own question:  a tip of the day]

When Whirr 0.6.0 spawns a Hadoop cluster (CDH  or Apache) for EC2, 
fs.default.name is set up with the public DNS of the master node.  When 
EC2 nodes talk to each other via private ip addresses, there is no 
charge for data transfer, but there is a charge for transfer over public 
ip addresses.

Is this limitation?

No, because DNS resolution inside the cluster returns a private ip 
address for a public DNS name like ec2*1.compute.amazonaws.com.  The 
*.compute.internal DNS name resolution returns the same private ip address.


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