Replace "drives" by "storage spaces".
You should not just create one big storage space for the guest.
You should create 6 or more for performance reasons.
Yes, when you do a CRTNWSSTG it will spread that over all the drives in
the ASP you create it.
However, the guest still needs 6 'logical units' or LUNs as they talk
about it in the SAN world.
You CAN do just 1. I have. Those lpars are also very slow.
Where do you see that your bottleneck is the lack of LUNs in performance
tools? I haven't a clue. I'm just standing on the shoulders of giants.