Data Center Design Raised Floor Versus Slab Floor.note¶
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We’ve updated this blog post for 2016.
SV5, Equinix’s newest data center in Silicon Valley, was designed using slab
floors.
In the data center industry, few topics raise more heated discussion than the
subject of raised floor versus slab floor construction.
Twenty years ago, the topic didn’t even come up in conversation – nearly all data
centers used raised floor construction.
However, in the last five to ten years, the debate has generated a wide variety of
whitepapers and analyses, including computational fluid dynamics (CFD)
modeling of cooling systems performance and new terminology to define cooling
effectiveness.
To further fuel the flames, various manufacturers of cooling systems and
equipment have attempted to end the debate once and for all, with one
manufacturer going so far as to claim raised floor data centers are obsolete.
As an operator of more than 90 IBXs globally, Equinix has a lot of experience
with the design, construction and operation of both types of data center. We
raised industry eyebrows when we built our first IBXs starting in 1998 – with
slab floor and overhead cooling rather than raised floor.
In the ensuing years, those IBXs have performed exceptionally well, particularly
in handling high power density (HPD) loads such as the first blade servers and
high-performance optimized compute platforms such as the Sun Fire
UltraSPARC boxes. While classic data centers were struggling to cool these
loads, our IBXs cooled them with ease.
Today, Equinix constructs both types of data centers. Why? The decision is
driven by business needs and market demands.
Data Center Design: Raised Floor Versus Slab Floor?
Dave PickutMarch 2, 2011
Check out the latest updates on Raised Floor vs. Slab Floor!
The business and operational needs for any data center or telecommunications
facility should drive the design. Factors other than cooling need to be considered,
particularly in a multi-tenant facility such as an Equinix IBX. While a data
center built for a specific purpose by a single owner or tenant can be optimized in
a variety of ways, a multi-tenant colocation facility has to meet a broad spectrum
of needs.
Our analyses have indicated that when it comes to cooling efficiency for base
design power density, neither design has a significant advantage. A pressurized
raised floor system delivering cooling air via perforated floor tiles consumes
about the same energy as pushing cooling air through overhead ducts and
diffusers. From a layout flexibility perspective, raised floor has an advantage
because perforated tiles can be easily rearranged. Overhead cooling, however,
has fewer issues with air leakage or air bypass. System air balancing is a little
more difficult with raised floor.
Construction cost comparisons also indicate that neither approach has a
compelling advantage. The various component costs associated with each
approach yield a similar cost per square foot of data center area.
Consequently, business needs become the deciding factor for one system versus
the other. For future flexibility in a multi-tenant facility, the raised floor approach
has an advantage.
The accessible raised floor plenum facilitates future changes such as added
cooling or electrical infrastructure – it is easier to run new conduits or piping
under a raised floor than it is to run overhead in a “live” data center. (Note: in our
IBXs with raised floor, we use the underfloor plenum primarily for air delivery
and routing of chilled water piping, if any. Power and data cabling are run
overhead. This result in an underfloor area with few obstructions). The
flexibility to run future services to HPD cooling equipment such as door coolers,
in-row cooling units, or heat transfer media direct to servers is important for
some facilities.
For equipment installation and movement, and overall maintenance cost, the
advantage goes to the slab floor. The concerns with point loading or moving
loads associated with raised floor systems are not an issue with a slab floor.
Maintenance costs for a slab floor are lower than those for a raised floor.
Seismic (earthquake) performance is also less costly for a slab floor. Equipment
anchoring is easier, and the added lateral bracing and reinforcement associated
with a raised floor system are not issues with a slab. Market demand is a factor
for a global operator like Equinix. In various regions of the world, the market
expects data centers to have raised floor. For that reason, some of our designs
incorporate raised floor – but still keep power, data and some cooling functions
(such as return air plenums for close-coupled cooling) overhead.
In summary, the best design for a data center is that which best fits the
operational and business objectives that have been identified. Let the debate rage
on.