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From Shu Zhang <szh...@mediosystems.com>
Subject RE: read repair across datacenters?
Date Mon, 27 Dec 2010 23:55:38 GMT
Brandon, for a read with quorum CL, a response is returned to the client after half (rounded
up) the replica nodes responds. Do you mean that those half are RR'ed before the response
is returned to the client and the other half RR'ed asynchronously? Or is it that the other
half of replicas are not RR'ed?

________________________________________
From: Brandon Williams [driftx@gmail.com]
Sent: Monday, December 27, 2010 3:00 PM
To: user@cassandra.apache.org
Subject: Re: read repair across datacenters?

On Mon, Dec 27, 2010 at 4:44 PM, Narendra Sharma <narendra.sharma@gmail.com<mailto:narendra.sharma@gmail.com>>
wrote:
The comment in the cassandra.yaml says:
"specifies the probability with which read repairs should be invoked on non-quorum reads"

Does this mean RR chance is applicable only for non-quorum reads?

Yes, because on quorum or greater the RR is performed before the response is returned.

Another question on same topic:
Will RR use one of the node in the other datacenter as coordinator instead of sending the
data to each replica (assuming they have old data)? This is to reduce the amount of network
traffic between datacenters.

https://issues.apache.org/jira/browse/CASSANDRA-1530

<https://issues.apache.org/jira/browse/CASSANDRA-1530>-Brandon

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