Hi, My service is not yet ready to be fully multi-DC, due to how some of my legacy MySQL stuff works. But, I wanted to get cassandra going ASAP and work towards multi-DC. I have two main cassandra use cases: one where I can handle eventual consistency (and all of the writes/reads are currently ONE), and one where I can't (writes/reads are currently QUORUM). My test cluster is currently 4 smalls all in us-east with RF=3 (more to prove I can clustering, than to have an exact production replica). All of my unit tests, and "load tests" (again, not to prove true max load, but to more to tease out concurrency issues) are passing now.
For production, I was thinking of doing: -4 cassandra larges in us-east (where I am now), once in each AZ -1 cassandra large in us-west (where I have nothing) For now, my data can fit into a single large's 2 disk ephemeral using RAID0, and I was then thinking of doing a RF=3 with us-east=2 and us-west=1. If I do eventual consistency at ONE, and consistency at LOCAL_QUORUM, I was hoping: -eventual consistency ops would be really fast -consistent ops would be pretty fast (what does LOCAL_QUORUM do in this case? return after 1 or 2 us-east nodes ack?) -us-west would contain a complete copy of my data, so it's a good eventually consistent "close to real time" backup (assuming it can keep up over long periods of time, but I think it should) -eventually, when I'm ready to roll out in us-west I'll be able to change the replication settings and that server in us-west could help seed new cassandra instances faster than the ones in us-east Or am I missing something really fundamental about how cassandra works making this a terrible plan? I should have plenty of time to get my multi-DC working before the instance in us-west fills up (but even then, I should be able to add instances over there to stall fairly trivially, right?). Thanks! will
