On Wed, Jun 2, 2010 at 10:39 PM, David King wrote: > If I go to fetch some row given the rack-unaware placement strategy, the default snitch and CL==ONE, the node that is asked is the first node in the ring with the datum that is currently up, then a checksum is sent to the replicas to trigger read repair as appropriate. Yes > So with the row cache, that first node (the primary replica) is the one that has that row cached, yes? No, it's the closest node as determined by snitch.sortByProximity. any given node X will never know whether another node Y has a row cached or not. the overhead for communicating that level of detail would be totally prohibitive. all caching does is speed the read, once a request is received for data local to a given node. no more, no less. -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of Riptano, the source for professional Cassandra support http://riptano.com