well, queue_depth and cmd_size would give you the number of I/O
operations the LUN can handle at given time, that number should not
exceed the number of I/O operations the controller can handle ( times
the number of controller but not exceed the number of I/O operations
you can perform at storage level )... So, there is no direct answer to
your question, it's more about what I/O you can generate at application
level to sutturate your disks and what's the nature of your
application. Some time you might get by having fewer LUNs and bigger
ones and have less disks to configur/monitor/etc, some times having
more LUNs ( well, there is a limit actually in both AIX and ESS ) of a
smaller size will give you advantage... Keep in mind the more LUNs you
make at storage and having several HBA will add more burden then help...