Got it. Failover Mode 4.
I am trying to connect a Mac (Mavericks) to a Clariion 4-240. It's using an ATTO external Thunderbolt fiber channel adapter. I have it zoned on the switch, and I manually registered it, created a storage group, and added it and the appropriate LUNs.  The problem is this. It can only see LUNs owned by one SP at a time in Disk Utility, and it seems random which SPs LUNs it sees. SPA has four and SPB has three. Sometimes when it boots up it sees three, sometimes four. If I go into the system info and look at fiber channel, it will indicate that there are seven LUNs visible, it just won't make them all available at once.  The only difference I can see between this and the other systems is getting Properties and going to the LUN Status tab, instead of seeing \\.\PhysicaDrive1, etc., all the Device IDs are listed as Unknown, and each LUN shows up twice.  I'm stumped, would appreciate any assistance
Manually Register a Mac