[jira] [Created] (CASSANDRA-6314) Cassandra sends multiple copies of data over WAN

["Robert Birnie (JIRA)" <ji...@apache.org>]

Robert Birnie created CASSANDRA-6314:
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             Summary: Cassandra sends multiple copies of data over WAN
                 Key: CASSANDRA-6314
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6314
             Project: Cassandra
          Issue Type: Bug
         Environment: RHEL 6.3, Cassandra 1:1.2.4-1, multi-dc environment
            Reporter: Robert Birnie
             Fix For: 1.2.4


Currently Cassandra seems to be sending data directly to all replicas in a multi-dc environment rather than to a datacenter specific coordinator node. I 

This should have been fixed in CASSANDRA-1530 (versions .7+). But with replication factor 1 for a keyspace in far DC we were sending 25Mbps over the WAN, then increasing the RF to 3 increased WAN traffic to 75Mbps.  Also, after a 10 hour test run with RF=3 an estimate of the data sent over the WAN very closely correlated with the data residing on the local disks.

I'm unsure what other versions this effects. If this is fixed somewhere already I would be highly interested but I can't find a Jira ticket regarding this. 



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