https://support.emc.com/docu32938_White-Paper:-EMC-CLARiiON-Asymmetric-Active-Active-Feature-—-A-Detailed-Review.pdf?language=en_US

The SAN is indeed active / active / active / active / and so on. Every port on every switch is always active.

Storage Arrays like Clariion and VNX however are still active / passive. This means only 1 Storage Processor owns a LUN. both SPs can own LUNs and are actively processing IOs from hosts, but each LUN is owned by only a single SP. With the use of ALUA hosts can access LUNs over both SPs, but the non owning SP will redirect IOs to the owner in the back end anyway, which causes these requests to be a bit slower than IOs going directly over the optimal path.

YOu should also provide what operating system you're using (when you say MRU and Fixed, you probably mean ESX, but you should provide the information to be more clear on your request).

If using ESX 4.x and higher and the array is running flare 30, then you set the failover mode on the array to 4 (ALUA) and on each ESX host you set the failover Policy to either Fixed_AP or Round Robin.

On PowerLink you can find documents called "EMC Host Connectivity Guides for xxxxx". Each one is for a different operating system.

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glen