Currently we run a 4-node Cassandra ring in each of two datacenters. We would like to rebuild them into a single 8-node ring. All else being equal we would really like to have consistent reads, so we currently run QUORUM reads and writes. However, if we lose a datacenter it appears that this would cause many or all requests to fail due to inability to meet the ConsistencyLevel. Since we plan to send requests to both datacenters, switching to LOCAL_QUORUM shouldn't be enough to guarantee consistency.
Cassandra appears to be sorely missing ConsistencyLevel settings that are measured against only available nodes.
What can be done to get maximum consistency without availability failures in this scenario, and what has to be traded-off to get it?