Raised Floors—Unnecessary Cost or Unparalleled Performance.note

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Raised Floors—Unnecessary Cost or Unparalleled Performance?

Posted by: on October 24, 2013

This week we have a post from a guest blogger! Chris Ouellette is a

Senior IT Specialist of Data Centre Services for IBM Canada, Ltd.

When constructing a new data center, companies nowadays are

invariably faced with the decision of whether or not to use a traditional

raised floor.

Those of us who have been around for a while recall early large

mainframe equipment that required bulky cables, which could only

realistically be placed under a raised floor. Other data center systems and

services that required bottom-fed access were also typically concealed

under the raised floor. Most importantly, the raised access floor was used

to deliver cooled air to the front of the equipment racks.

But times have changed. Convergence has reduced cabling loads and

bundles of optical fiber cables can now be installed in overhead trays or

below the raised floor. The smaller footprint of today’s computing

equipment allows for installation in standard EIA-310 racks. Equipment is

also more powerful and cooling requirements have increased. Rather

than traditional perimeter cooling, close-coupled cooling brings cooling

closer to the equipment, often in line within rows for increased energy

efficiency.

While these innovations have made it possible to potentially do away with

raised floors, is the decision really that straight-forward? There are

several criteria to consider.

Cooling System

Will CRAC units be perimeter, in-row, overhead or a hybrid solution?

Reconfiguring floor tiles to maximize airflow patterns and ensure cold and

hot air separation is easier than changing overhead duct work. Plus,

overhead ducting can complicate cable tray routing and other systems.

Locating chilled water pipes overhead is also more problematic should a

leak ever occur.

Equipment Requirements

How will power be brought to the rack? If overhead power is used, all the

devices must be able to connect. Large enterprise devices like disk

arrays and tape libraries might require power cords to exit the bottom of

the rack, and some of these large power cords can be rather unsightly or

present a trip hazard in a non-raised-floor environment. Some equipment

may also have different airflow needs (i.e., top or side vented), which is

easier to accommodate when the underfloor space is used as a cooling

plenum.

Electrostatic Discharge and Grounding

The simple act of walking across a floor can generate a detrimental static

charge. Raised-floor tiles are designed to properly direct these charges to

ground—and they resist static electricity in the first place. Non-raised-

floor environments require anti-static solutions such as special tiles with

conductive adhesives and copper ground straps. Furthermore, best

practices require bonding equipment racks to ground to keep high-

frequency noise away from critical processing equipment—a task that is

typically easier in a raised-floor environment since the floor’s support grid

provides an ideal low impedance path.

System Location

Some services like floor drains and water pipes are naturally predisposed

to be in a certain location. With a raised floor, drains can be strategically

placed to accommodate condensation lines. They also provide a way to

get rid of water should a leak occur. While power and communication

cables are equally at home underfloor or overhead, some prefer to keep

work on ladders to a minimum due to safety concerns.

Change Management

While floor choice doesn’t impact changes within the racks, when an

entire rack or row needs to be repositioned, a raised-floor’s fixed systems

(i.e., cooling and power) can typically stay in place. In a non-raised

environment, changing rack or row placement could require changing

overhead infrastructure, including air ducts, cable tray and power bus

systems.

Space Considerations

A raised floor can require additional space and either ramps or a sunken

slab to accommodate difference in floor height with surrounding areas. In

spaces with very low ceilings, a raised floor may not be possible if the

minimum vertical clearance of 8’-6” cannot be maintained. A non-raised-

floor environment does offer more flexibility regarding rack and row

placement since they do not need to line up with tiles. While this may

allow for more racks, air management challenges could be created.

Cost

The potential cost of a raised floor (typically $20-$25 per square foot)

should also be considered. But without a raised floor, the cost of installing

an anti-static floor ($7-$12 per square foot) should be factored into the

equation. In fact, all factors should be considered before determining if

the cost differential alone is enough to make a decision.

There is no single flooring solution that will satisfy every need. While

doing away with a raised floor can be justified in some situations—

especially where space and cost are a primary concern—it’s important to

be fully aware of all the limitations this decision could create. There are

few, if any, limitations to what type of IT equipment and cooling systems

can be accommodated using a raised-floor system.