1. The Best Use of Space
The space beneath a raised floor offers a variety of data center design advantages. The space between the floors acts as a plenum through which air conditioning flows and is distributed above by placing perforated tiles to direct the cool air. Because the tiles can be easily shifted, the cool air can be shifted to accommodate different rack configurations. Cable can also be ran beneath the floor eliminating the need for cable trays and leaving the maximum amount of overhead space. The downside to placing cables beneath the floor is that they are not easily accessible. This creates a problem with changing IT in the data center. The designer has the option of installing cable racks overhead, or taking on the inconvenient task of rewiring beneath the floor.
2. Data Center Layout
Slab flooring bolts racks and equipment directly to the floor. With racks already bolted into the floor, and cooling aisles are already established, it is more difficult to rearrange the space to accommodate tenants in a colocation. With raised flooring, the tiles can be easily relocated to accommodate a diverse set of individual needs. Racks can be relocated easily, which is ideal for colocation data centers with a base of tenants whose individual needs constantly change. A data center with slab floors is limited in different layout possibilities.
3. The Weight Factor
Slab floors data center designs have an advantage over raised floors because the racks are bolted directly to the floor. A slab floor has virtually no maintenance cost when comparing to a raised floor. With a raised floor, there are maintenance costs associated with point loads and casters to balance out the weight. In addition to those costs, a raised floor requires added lateral bracing of the racks. These costs will potentially vary over time. As IT advances, every two years the hardware gets denser and thinner. This allows data centers to condense more equipment into the same space that bulkier, obsolete equipment once occupied. When comparing these costs to the advantages of directly bolting equipment into a slab floor, the future plans of the data center must be considered.
4. The Cooling System
With slab floors, overhead cooling is the most widely used option. With raised floors, the cool air passes through the plenum and is directed to the racks through grated tiles. With raised flooring, these tiles can be moved around to specifically direct cool air to IT equipment. With an overhead cooling system, more vents can be added but cool air cannot be as easily directed to the equipment. Overhead cooling also has fewer issues with air leakage or bypass. Conversely, with raised floors, cables and pipes can obstruct the space in the plenum which can constrict the ability for cold air to circulate adequately. This can only worsen if cables have been continuously ran to update IT.
Raised floors pose more security risks than slab floors. Some states require the racks to be directly bolted to a slab floor. With raised floors, racks are anchored to the secondary surface. This creates an unpredictable outcome in the event of seismic activity, which is not ideal in areas prone to earthquakes. Another security problem with raised floors is that they collect dirt and debris beneath the surface that requires extra cleaning. Alarms can be set off from the dust accumulation. This isn’t a factor with slab floors which are much easier to keep clean.
When considering these five issues, both raised floors and slab floors have advantages for some designers and drawbacks for others. The debate may go on for some time about which is the better data center design. At the end of the day, the decision of which to install in a data center comes down to the immediate needs and future plans of the individual company.