Hi,
There are couple of things you should keep in mind, here.
I am assuming that there is no ISL between the 2 switches.
1) Earlier since you had A/P firmware, and had 2 paths from each host to the MSA, neways one path was leading to a passive controller and thus was not seeing any LUNs, therefore only one path was active at a time, now because you have an A/A firmware, both the controllers can see the LUNs, thus you need to have a multipathing software on your Host Machines, eg: MPIO.
MPIO gives you an oppurtunity to do either Load balancing or choosing one of the 2 paths to do I/O
This is where the second point comes in the picture.
2) If you have both the Controllers on the MSA as active, have you enabled Prferred path settings? if you have then that leads to Explicit A/A configuration. which means, that one specific controller will manage some specific set of LUNs.
Now lets assume that if the I/O is happening from a 1st FC-HBA of a Host leading to Controller 1 of the MSA, but the LUN you are trying to acees is managed by Controller 2 (because of the explicit prefered path configuration in ACU), then Controller 1 has to communicate to Controller 2 through the Inter Controller Link and to talk to the LUN. now since Inter Controller Link is a serial communication, thus this could be a reason for the bottleneck.
Changing the the settings in HBA, should not make any difference. I would suggest to disable the Preffered path selection (not SSP-selective storage presentation) in ACU, or , Manage the same using the Multipathing software in such a way that it matches your prefered path selection.
