Equipment weight and tile strength

The process of building a data-center facility appears to be simple on the inception but has several aspects that must be done correctly. In this book excerpt, find out how to get it done right the first time.

The following 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.

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 facilities.
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.
Historically most tiles are made of concrete with a steel shell. Perforations in the concrete weaken the tile. When equipment is rolled along the aisle, the perforated tiles are temporarily subjected to static load and, therefore, must have adequate static load rating. Strength of cast aluminum tiles are not undermined by perforations and are, therefore, preferable to concrete tiles.

Electrical Wireways

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.

Cable Trays

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

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