Equipment Weight and Tile Strength
One of the central issues impacting data center design is the weight, power,
and cooling requirements of the equipment located therein. This section discusses
the effect of size and weight of the equipment on design of floor tiles.
Chapter 7 covers the effect of power requirements on the design of data-center
First, it is important to assess the present and future load on the raised floor. Once the data center is functional, changing the raised floor is close to impossible and rarely done in practice. It is an arduous and expensive task in terms of both time and money. Knowing the approximate weight of equipment is a prerequisite to a good design of the stretcher system in the subfloor plenum and quality of tiles. There are two types of load:
- Point load— Most equipment or racks sit on four rollers, casters, or feet. The load on any one of these four feet is called point load. For example, an IBM p690 server weighing 2,600 pounds has a point load of 650 pounds on each of its feet. If its feet rest on 1 square inch, the tile must be capable of bearing 650 pounds on 1 square inch without deflection of more than 1 or 2 mm.
- Static load— The sum of all point loads on the tile. If each of two racks (or stand-alone equipment) with point loads of 700 pounds per feet have one foot on a particular tile, that tile will be subjected to a total of 1,400 pounds. The tile must therefore be rated for 1,400 pounds of static load.
A wireway is a long metal box containing electrical wiring and power outlets
for equipment. It is usually located below the tiles (or panels). The power
cords from servers and devices in the data center are routed through cutouts in
the tiles to these power outlets. The outlets are, in turn, connected by electrical
wiring to circuit breakers and subpanels. Alternatively you can run power
cables directly from each breaker (in a subpanel) to the floor. But this would
create two problems: They obstruct air flow in the plenum (thereby decreasing
air pressure), and they create a mess of cables.
Electrical wireways help centralize power distribution to few areas. Additionally they help secure power outlets (otherwise, they would be swinging around in the air). The smaller the electrical wireway, the less is its blockage to air flow. But electrical wireways must also meet city electrical codes.
It is common practice to route the power cables from equipment in the data
center through cutouts in the tiles to outlets in the under-floor plenum. A large
number of such cables create disarray. It is difficult and time-consuming to
trace bad cables. The pandemonium of cables obstructs air flow and decreases
air pressure in the plenum.
Cable trays help reduce the cable mess. They are U-shaped wire baskets that
usually run parallel to the wireways and contain the length of the cables. The
cable lengths snake along the cable tray to the power outlets. Besides power
cables, the trays also contain network and storage cables. Cable trays are not
necessary but are useful.
The cable tray should not be placed very close to the bottom of the raised floor tile. Optimally cable trays must be at least 2 inches below the bottom of the tile. It is also important that the wireway and outlets be accessed by removing only one or two tiles.
Design and Plan Against Vandalism
For most organizations, online data is one of their most expensive assets. All
business-critical information is stored online and must be protected from sabotage,
vandalism, and so forth. The data center must be selected in a building
or neighborhood where it is easy to control access. Check for existing doors,
windows, or ventilators that open to the outside and uncontrolled areas. If
they are not necessary, replace them with walls. If they are necessary, you must
install alarm systems and motion detectors. However, it is best to locate the
data center in the interior of a building so that it has no exterior doors or windows.
When designing a new area, plan for one (or, at most, two) entrances to
the data center.
The design must include various monitoring devices. Install surveillance
cameras at various locations, especially at entrances, such that they record the facial view of those entering the area. Motion detectors and alarms must be
installed at various locations. If data-center space is shared with other companies,
each company must have separate areas with physical barriers.
Make provisions for emergencies. Keep equipment-safe fire extinguishers at
a few locations.
You must protect the equipment and data not only from external intrusions
but also from internal elements. Disgruntled employees are a common cause
of vandalism. Only employees who need access must be granted it. Untrained
personnel can create security risks, and they must be kept away from critical
areas of the data center.
The previous tip was excerpted from Chapter 4, 'Data Center Design,' from the book Administering Data Centers: Servers, Storage, and Voice over IP by Kailash Jayaswal, courtesy of Wiley Publishing. Click here for the complete collection of book excerpts.
This was first published in May 2006