On: Postgres-XL: Scalable Open Source PostgreSQL-based Database Cluster

[laggyluke]

This sounds like a split-brain disaster waiting to happen, when a network partition between the two load balancers makes both think that the other one is down.

[regularfry → laggyluke]

This is why you only ever automatically fail over in one direction, and (ideally) can STONITH.

[annnnd → laggyluke]

I was running a similar system. What solution would you propose?

[laggyluke → annnnd]

I'm no expert, but I think the main idea is to have an odd number of nodes plus a consensus protocol like Paxos or Raft to figure out who's actually alive. If a node finds itself in a split minority, it won't become a master. This doesn't work when you have only two nodes, as there's no minority after the split, both sides are equal. Building this from scratch is extremely difficult and error-prone, so people usually use systems like ZooKeeper.