incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Eben Hewitt <eben.hew...@gmail.com>
Subject Re: what is DCQUORUM
Date Wed, 12 May 2010 14:03:42 GMT
QUORUM is a high consistency level. It refers to the number of nodes that
have to acknowledge read or write operations in order to be assured that
Cassandra is in a consistent state. It uses <ReplicationFactor> / 2 + 1.

DCQUORUM means "Data Center Quorum", and balances consistency with
performance. It puts multiple replicas in each Data Center so operations can
prefer replicas in the same DC for lower latency.

See https://issues.apache.org/jira/browse/CASSANDRA-492 for a little
discussion.

Also see
http://svn.apache.org/repos/asf/cassandra/trunk/src/java/org/apache/cassandra/locator/DatacenterShardStrategy.java
 and
http://svn.apache.org/repos/asf/cassandra/trunk/src/java/org/apache/cassandra/service/DatacenterWriteResponseHandler.java

Eben



On Wed, May 12, 2010 at 6:15 AM, vd <vineetdaniel@gmail.com> wrote:

> Hi
>
> I have read about QUORUM but lately came across DCQUORUM. What is it  and
> whats the difference between the two ?
>
>


-- 
"In science there are no 'depths'; there is surface everywhere."
--Rudolph Carnap

Mime
View raw message