How to represent floors in a building

AutoCAD Map 3D can do floor plans - use it to create 2D and 3D floors - then floors lead to racks (servers) and racks go to device.

Each level can be pulled out in to reveal floorplans with all the equipment locations.

One method is to create layers for each individual floor. You can turn layers on and off to see the respective floors. It probably would be a good idea to have a separate layer for the external walls or the footprint, which you can use while drawing internal walls at the different levels.

If you just need 2D symbology, simply add an integer numeric field and enter the number of floors in it. You can either use symbology and/or labels to indicate the floor number. If you have access to the 3D analyst, the previous procedure can also be used, but I would use height instead. In this way, you can extrude the building height above a surface getting a fairly useful representation of buildings (sans roof) in a landscape if draped over a DEM.