Hello dev@, We'd like to propose CEP-58: Satellite Datacenters for adoption by the community. CEP-58 proposes adding satellite data centers as an alternative to the 3 full DC topology for achieving multi-DC high availability. Satellites are small witness only datacenters (~1/15th full DC size) that replicate the mutation journal, but otherwise don’t run the storage engine. This enables transactionally consistent HA (via failover) with just 2 full DCs and one satellite DC.
This feature benefits users running clusters in a 1 or 2 DC topology for cost or latency reasons, and is especially beneficial for paxos heavy workloads, since only one of the paxos messages needs a satellite round trip. When used in conjunction with witness replicas in the full DCs, single DC clusters could become HA for less than the cost of adding a second datacenter. The CEP is linked here: https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-58:+Satellite+Datacenters, but please keep the discussion on the dev list. Thanks! Blake Eggleston
