> hence you need to query _all_ the nodes or can end up in a split-brain situation and lose consistency (or availability if you choose to down the system or a part of the system).
No.Depending on the type of consensus algorithm you can get away with reading from a majority or nodes or even less: for example in a Multipaxos system you just read from the master.
One side of the partition has quorum and the other does not.
Processing keeps happening on the partition with quorum.
A practical example I worked on is Google's Photon; multi-region logjoining with Paxos for consistency. When the network caused a region to become unavailable all the logjoining work happened in the other regions. Resources were provisioned for enough excess capacity to run at full speed in the case of a single region failure and the N-region processing allowed the redundancy cost to be as low as 100%/N overhead.
No.Depending on the type of consensus algorithm you can get away with reading from a majority or nodes or even less: for example in a Multipaxos system you just read from the master.