We have a smaller datacenter that is located in an older facility. (This building was built back in the 40's or 50's) Does it matter if I run UTP or STP through my racks? It may not matter but the cable for backbone running from my isp to my network is cat5 UTP running through the ceiling that is really old and there is a ton of florescent lighting and such that goes with the run. Any advice?
Shielded cable can significantly reduce interference, which can also mean that the signal quality may degrade less over a distance. Within the same rack, shielded cable is probably overkill. You're going to get the same local gigabit connection with Cat5e as with shielded Cat6.
Shielded cable comes with some grounding requirements. Not grounding the devices properly can cause some trouble, mainly if the devices at the ends aren't using the same grounding source. This is usually more of a problem going between buildings, but in older construction, who knows how (or even if) electrical grounding has been implemented. Improper or missing grounding is serious business. I've seen entire racks of machines spontaneously and randomly lock and reboot simply because they weren't properly grounded.