What is the latency between the links (used by corosync) ?
e,g,
NodeXinDC1 to NodeYinDC2 latency in ms/ns
NodeXinDC1 to NodeZinDC3 latency in ms/ns
NodeYinDC2 to NodeZinDC3 latency in ms/ns
Are you using a "Virtual Private Network" technology to tie the underlying network together, created a...