The only way I can think of would be to use NetworkTopologyStrategy and PropertyFileSnitch to define two data centers.  Set node1-node3 in DC1 then set node4 in DC2.  Then set the strategy_options=[{DC1:3, DC2:1}] for that keyspace.

This would make your cluster conceptually similar to a split datacenter as described in the Brisk white paper.

References:

http://www.datastax.com/docs/0.7/operations/datacenter
http://www.datastax.com/wp-content/uploads/2011/03/WP-Brisk.pdf

Robert Jackson


From: "A J" <s5alye@gmail.com>
To: user@cassandra.apache.org
Sent: Monday, May 2, 2011 1:26:31 PM
Subject: Specifying exact nodes for Consistency Levels

Is it possible in some way to specify what specific nodes I want to
include (or exclude) from the Consistency Level fulfillment ?
Example, I have a cluster of 4 nodes (n1,n2,n3 and n4) and set N=4. I
want to set W=3 and want to ensure that it is n1,n2 and n3 only that
are used to satisfy w=3 (i.e. n4 is excluded for w=3 calculation).

Thanks.