why kubernetes HA need odd number of master

Question

I have kubernetes HA environment with three masters. Just have a test, shutdown two masters(kill the apiserver/kcm/scheduler process), then only one master can work well. I can use kubectl to create a deployment successfully ,some pods were scheduled to different nodes and start. So can anyone explain why it is advised odd number of masters? Thanks.

Answer 1

Because if you have an even number of servers, it's a lot easier to end up in a situation where the network breaks and you have exactly 50% on each side. With an odd number, you can't (easily) have a situation where more than one partition in the network thinks it has majority control.