This morning, Rob and I tested the redundant links between our fibre channel switches in ECS and PP. Everything went off without a hitch, and that's good considering that we were dealing with live traffic!
We have two dual switch clusters in ECS. There are two fibre channel links between the clusters, one from each switch. There is an additional single switch in the blackboard server rack which has one link to each cluster... so basically it straddles the two clusters.
We also have one dual switch cluster in PP, and both switches in that cluster has a connection to one of the two clusters in ECS.
So we pulled the two direct links between the ECS clusters, and traffic failed over to the blackboard switch and went through that.
We then pulled the connection to the blackboard switch, and then traffic predicably failed over to going to, and then back out from the switch cluster in PP.
This means it'll take a lot of things going wrong to split the fabric.... we can survive two switch failures without splitting the fabric. This testing also confirmed that we have a correct fibre channel zone configuration (fibre channel zones are analogous to VLANs on a ethernet network)