Mobile pallet racking is by far the most space efficient racking system. The racking itself is standard wide aisle pallet racking, however with the addition of mechanical bases to move the entire rack, either a length at a time or moving large sections of the racking.
This eliminates the need for aisles between the racking thus massively reducing the footprint required. This serves a dual purpose as you can condense your existing storage to take up as little as 50% of the original floor space OR nearly double the amount stored in the same foot print area.