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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: Multi data center configuration - A question on read correction
Date Thu, 16 Jun 2011 07:48:43 GMT
Yes, that's the way to do it.

On Wed, Jun 15, 2011 at 9:43 PM, Selva Kumar <wwgselva@yahoo.com> wrote:
> Thanks Jonathan. Can we turn off RR by READ_REPAIR_CHANCE.= 0. Please
> advice.
>
> Selva
>
> ________________________________
> From: Jonathan Ellis <jbellis@gmail.com>
> To: user@cassandra.apache.org
> Sent: Tue, June 14, 2011 8:59:41 PM
> Subject: Re: Multi data center configuration - A question on read correction
>
> That's just read repair sending MD5s of the data for comparison.  So
> net traffic is light.
>
> You can turn off RR but the downsides can be large.  Turning it down
> to say 10% can be reasonable tho.
>
> But again, if network traffic is your concern you should be fine.
>
> On Tue, Jun 14, 2011 at 8:44 PM, Selva Kumar <wwgselva@yahoo.com> wrote:
>> I have setup a multiple data center configuration in Cassandra. My primary
>> intention is to minimize the network traffic between DC1 and DC2. Want DC1
>> read requests be served with out reaching DC2 nodes. After going through
>> documentation, i felt following setup would do.
>>
>>
>> Replica Placement Strategy: NetworkTopologyStrategy
>> Replication Factor: 3
>> strategy_options:
>> DC1 : 2
>> DC2 : 1
>> endpoint_snitch: org.apache.cassandra.locator.PropertyFileSnitch
>> Read Consistency Level: LOCAL_QUORUM
>> Write Consistency Level: LOCAL_QUORUM
>>
>> File: cassandra-topology.properties
>> # Cassandra Node IP=Data Center:Rack
>> 10.10.10.149=DC1:RAC1
>> 10.10.10.150=DC1:RAC1
>> 10.10.10.151=DC1:RAC1
>>
>> 10.20.10.153=DC2:RAC1
>> 10.20.10.154=DC2:RAC1
>> # default for unknown nodes
>> default=DC1:RAC1
>>
>> Question I have:
>> 1. Created a java program to test. It was querying with consistency level
>> LOCAL_QUORUM on a DC1 node. Read count(Through cfstats) on the DC2 node
>> showed read happened there too. Is it because of read correction?. Is
>> there
>> way to avoid doing read correction in DC2 nodes, when we query DC1 nodes.
>>
>> Thanks
>> Selva
>
>
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of DataStax, the source for professional Cassandra support
> http://www.datastax.com
>

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