As DESigner this question is arising more often from the end user, of course it is still a common use to have this system in actual data centre.
Before any answer I rather prefer to analyse the type of DC that I am DESigning what GRC, sustainability and Energy efficiency parameters my customer has or want to get in day ONE and after.
More and more DESigns include PODs, containerized and/or modular spaces where temperature/humidity have differential areas. Not only in COLO but also in Enterprise facilities. So it is a possibility to have a computer hall with raised flooring and next to it a hall without it.
Because the old mainframes needed water cooling pipes this kind of floor was developed to accommodate such pathways, also communication & electrical ones took advantage of such plenum. But then few years ago the old thermal loads started to increase, increase increase......An dour old friend become with old the obstructions (wire/cable) and short deep not a solution but part of the cooling problem for such thermal loads.
Then several vendors set the containers, InRow, liquid, chimneys and several other cooling solutions that are worth to use and can avoid using the raised floor. So the DESigner should take out from data centres facilities or not.
My perception and experience is that it will depend on DC by DC solutions, heigth available between floor and ceiling, safety/security, IT Transport, Electrical distribution (whips or busways) but as ultimate decision from the end customer/OPErator´s "style" and preferences.
So you can set a POD solution and still have a raised floor or get containerized cabinets (all in one) and avoid using such flooring.
Or what do you think?
Roberto Sanchez, RCDD