[ClusterLabs] Pacemaker/corosync behavior in case of partial split brain

[Andrei Borzenkov]

Three nodes A, B, C. Communication between A and B is blocked
(completely - no packet can come in both direction). A and B can
communicate with C.

I expected that result will be two partitions - (A, C) and (B, C). To my
surprise, A went offline leaving (B, C) running. It was always the same
node (with node id 1 if it matters, out of 1, 2, 3).

How surviving partition is determined in this case?

Can I be sure the same will also work in case of multiple nodes? I.e. if
I have two sites with equal number of nodes and the third site as
witness and connectivity between multi-node sites is lost but each site
can communicate with witness. Will one site go offline? Which one?