I would recommend that you try to stagger your backup and AO windows so that they do not step on each other, unless you have a heavy surplus of horsepower to slug through that simultaneous workload (sounds like you don't).
You may want to double-check that your AO measurement interval does not include backup/AO windows as well.
For a good start, check out
this PDF posted by Afidel:
https://docs.google.com/file/d/0B-0rqB4 ... c1YVE/editIt's not official customer facing HP documentation, however it appears to be what HP professional services use when they manage a 3PAR for their customers.
Some that I have been using:
15k drivess > 180 iops (count 3)
7.2K drives > 80 iops (count 3)
ports > X kbps where x= 80% throughput
vlun > 40ms service time, count3, minimum_iops>50 (This is a new one I am still tuning)