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 <vineetdan...@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
