On Wed, Jun 2, 2010 at 10:39 PM, David King <dk...@ketralnis.com> 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
