What's filling the space in the warehouse is an important question, and what type of clients who need wireless access is another? If you have steel racks filled with dense products, you might need a couple APs at the floor level too, at alternate ends of different racks. If you have wide open space, you might only need a couple APs in the ceilings, and R710 would have good range for that purpose. How long is the warehouse, are there any machines or electrical things that could cause interference? Are your users carrying hand-held scanners or are they driving fork-lifts? Please share more details.