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From aaron morton <aa...@thelastpickle.com>
Subject Re: High bandwidth usage between datacenters for cluster
Date Mon, 29 Oct 2012 07:52:40 GMT
Outbound messages for other DC's are grouped and a single instance is sent to a single node
in the remote DC. The remote node then forwards the message on to the other recipients in
it's DC. All remote DC nodes will however reply directly to the coordinator.

> Normally this isn’t an issue for us, but at times we are writing approximately 1MB
a sec of data, and seeing a corresponding 3MB of traffic across the WAN to all the Cassandra
DR servers.

Can you break the traffic down by port and direction ?

Cheers



-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 28/10/2012, at 12:18 PM, Bryce Godfrey <Bryce.Godfrey@azaleos.com> wrote:

> Network topology with the topology file filled out is already the configuration we are
using. 
>  
> From: sankalp kohli [mailto:kohlisankalp@gmail.com] 
> Sent: Thursday, October 25, 2012 11:55 AM
> To: user@cassandra.apache.org
> Subject: Re: High bandwidth usage between datacenters for cluster
>  
> Use placement_strategy = 'org.apache.cassandra.locator.NetworkTopologyStrategy' and also
fill the topology.properties file. This will tell cassandra that you have two DCs. You can
verify that by looking at output of the ring command.  
>  
> If you DCs are setup properly, only one request will go over WAN. Though the responses
from all nodes in other DC will go over WAN. 
>  
> On Thu, Oct 25, 2012 at 10:44 AM, Bryce Godfrey <Bryce.Godfrey@azaleos.com> wrote:
> We have a 5 node cluster, with a matching 5 nodes for DR in another data center.   With
a replication factor of 3, does the node I send a write too attempt to send it to the 3 servers
in the DR also?  Or does it send it to 1 and let it replicate locally in the DR environment
to save bandwidth across the WAN?
> Normally this isn’t an issue for us, but at times we are writing approximately 1MB
a sec of data, and seeing a corresponding 3MB of traffic across the WAN to all the Cassandra
DR servers.
>  
> If my assumptions are right, is this configurable somehow for writing to one node and
letting it do local replication?  We are on 1.1.5
>  
> Thanks


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