http://blog.colovirt.com talks about this recent FC switch problem, if you using FC switches, then worth the read. Please read the full post for examples.
A few days ago there was in error on one of our Cisco MDS 9120 fiber switches. The current environment at this datacenter consists of two Cisco MDS 9120 SAN switches with servers redundantly connected between the two. These switches are used to connect the servers to our fiber channel (FC) storage systems. In this case, the servers are generally mapped to an EMC, NetApp, and two RamSans. Below outlines a basic example of what can be expected from multipathing and the Linux environment when there is loss of connectivity to one leg of the fiber network.