– Ken Koty, sales engineer for PDU Cables and former data center facilities manager for Thomsen Reuters, says:

When I’m talking with people about data centers, the discussions cover a wide range of topics.  One topic that comes up periodically is the benefits of raised floors, including raised floor vs. overhead cabling.  While cases can be made for both methods, my experiences involving renovations, new construction and consolidations of data centers has left me strongly in the camp for raised floor data centers and a preference for under floor cabling. 
I’m not here to try and tell you that one way is better than the other, when the time came to build our new data centers, raised floors were the only option we seriously considered.  Why?  Raised floors have always been and continue to be the dominant choice in data centers.  As a company, we had extensive experience with raised floors, I knew them, my staff knew them, and our IT department knew them.  Since raised floors are the industry standard, we had more options for integrating infrastructure components into our data center around a raised floor than if we built our data center on a slab. 
Our choice of using raised floors placed us with the majority of all data centers worldwide, and provided flexibility and scalability.  Because of the many benefits of a raised floor, we never regretted our decision.    
That said here are some distinct benefits that a raised floor offered our data center that I’d like to share with you. 
Flexibility – Scalability

After 30+ years working in data centers, I’ve seen all types of innovations in equipment.  What started out as large mainframes, card readers, and disk/tape drive memory machines, evolved into routers, servers and tablet computers.  I have more memory and computing power in my smart phone than we had in our entire data center (computer room) 40 years ago.  The one thing that hasn’t changed over the years is change itself, that and our use of raised floors as a platform.  The raised floor was easy to configure to accommodate moves, add-ons and changes.  Its flexibility allowed for retrofits of next generation devices into the existing floor space.   Even with increasing density the raised floor was always able to accommodate diverse heat loads throughout the facility. 
Without a raised floor, power to the racks must be run overhead using a bus system, and I’ve always been leery of bus systems and the fact that they tend to be proprietary, expensive and inflexible; once committed to a bus system you have limited options.   A short in a under floor power cord or PDU could take out a single rack, but a short in the bus system could take out the entire feed, and dozens of racks along with it.  Repair or replacement to a bus system could be a significant burden to a redundant power system. 
Utilizing an under floor plenum based cooling system always afforded me the opportunity to implement additional overhead cooling solutions to incorporate redundant cooling strategies if necessary.  With newer construction, we always planned for the deeper raised floor to provide a bigger plenum, which afforded us more flexibility and scalability for future needs. 
Cabling

Raised floors provide a distribution path for power and data cabling without the use of a ladder or enhanced structural cable trays or ceilings.  Cabling overhead requires access in and around overhead structures like ductwork and sprinkler heads as well as multiple people and the use of a stepladder to install and maintain cables.  I always felt that there was more risk of an accidental disconnect from an overhead cabling mishap than under floor.  If any cabling has to be done overhead, it’s best left to data cables, but my preference is to run both under floor.   
As long as cables are run in the hot aisle, power and data cables can run in the same space, under a raised floor, this allows you the flexibility to terminate the cables whenever and wherever you need them.
Typically utilizing a raised floor meant ceiling heights and other overhead obstacles where no longer issues, making the raised floor a preferred place to run power and data cables, based on flexibility, accessibility and capacity. 
The raised floor provided a built in ground grid for grounding of equipment, and water distribution lines placed under a raised floor present less risk in the event of water leaks.
Airflow Management

With the addition of dampers, integrated fans and directional airflow floor panels, the raised floor provides a perfect platform for supplemental cooling devices for optimal airflow control on an individual rack-by-rack basis. 
Hot/cold aisle containment is a best practice that needs to be considered for any higher density data center.  With a raised floor there is nothing faster and easier to implement than aligning floor panels into hot and cold aisles providing air containment without walls or structures. 
You can control vents from a raised floor concentrating cooling exactly where you want it, giving you more direct control over what spots in a room are cooled.  
If an area of the data center, or even a rack was running hot, rearranging or replacing a floor tile with a higher air flow version would often address the problem. 
Aesthetics

I took a lot of pride in the appearance of my data centers and being able to run cabling, both power and data, under floor to keep my interior space clean and neat was important.  Raised floors provide the kind of aesthetics that earned me many accolades from both management and customers.  I wasn’t the least bit embarrassed to offer tours of the data center.   
I also hate working in the dark and with overhead wiring systems, both power and data cables, they tend to run under the light fixtures and cast shadows over the cabinets and work area.  Running the cables under the raised floor allowed me to keep the data center clean and bright. 
Summary

A raised floor data center can accommodate large volumes of wires, cables and other services while cooling increasing heat loads.  Raised floor data centers have the ability to quickly deploy future technological and cooling advancements. 
Because raised floors are flexible, adaptable and scalable, capable of meeting a data centers current and future needs, raised floor data centers will continue to evolve and retain their position as the leading design platform for data centers for years to come.