Options for storing pallet in a warehouse include (from least expensive to most expensive): selective pallet rack, drive in rack, push back rack and pallet flow rack. As you can guess the density and efficiency becomes greater as the price goes up.
Selective pallet rack gives you access to all pallet loads from the floor but is not very dense because of required aisles. Drive in rack offers very dense pallet storage but is not very efficient because you have to drive your forklift into the rack system and back out with pallet on forks. Pushback rack offers you both density and efficiency because pallets flow on carts to the front of the system for fast picking. Pallet flow rack is the most expensive but it offers you not only density and efficiency but is the purest form of FIFO (First in First Out).
You have to ask yourself how many pallets per SKU (Stock Keeping Unit) do you have and how quickly do your pallets move in and out of the rack. Does your need for density and efficiency justify the cost of the rack. You may also find that the most flexible option may be storing pallets on stack racks.