On Fri, Feb 18, 2011 at 12:00 AM, Stu Hood <stuh...@gmail.com> wrote: > But, the reason that it isn't safe to say that we are a strongly consistent > store is that if 2 of your 3 replicas were to die and come back with no > data, QUORUM might return the wrong result.
Not so. If you allow vaporizing arbitrary numbers of machines without a trace then only systems that block for all replicas on each update could be considered strongly consistent, and I don't know of any systems in the wild that actually do that. Certainly other systems commonly considered "strongly consisent" like HBase do not. > A requirement of a strongly consistent store is that replicas cannot begin > answering queries until they are consistent The system as a whole can be consistent even if an individual replica is not; that is the point of CL > ONE. -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
