Manage data center density: proper planning and best installation practices are important for efficiency and growth

Communications News,  Jan, 2008  by Kamlesh Patel

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Managing growth in the data center is not as simple as installing new servers and racks. There really is a limit to the number of ports that can be added before the ability to reconfigure, upgrade, and replace network elements is hampered. Proper planning, best installation practices and the deployment of strategic solutions that help manage density while minimizing maintenance hassles also should be considered.

With the cost to build a data center reaching upwards of $1,000 per square foot, maximizing floor and pathway space is a critical aspect of planning for density. When planning a data center, design for the maximum cable densities of a fully deployed system.

The first step in planning is to remember that data centers may need to be expanded in the future and should therefore be located so that surrounding space can be easily and inexpensively annexed. Once the best location for the data center has been determined, the data center itself should be designed with ample areas of open floor space that can be easily reallocated to a particular function, such as a new equipment area.

The space should also be divided into specific functional areas that make the data center easily adaptable to changing requirements and growth. The TIA-942 standard for data centers is a useful set of guidelines for strategically locating functional areas of the data center.

Pathway space, both between functional areas and within the cabinets, should also be taken into consideration during the planning stage. When too many cables are routed in a single pathway, tracing an individual cable from one point to another can become difficult, and the probability of damage to the cables increases, leading to decreased network reliability and increased time to reconfigure the network.

CABLE BEND LIMITATIONS

A key step in estimating the proper amount of pathway space is to follow the industry cable fill rates, which specify the amount of cabling that can be installed in a pathway or space, while still preserving the integrity of the cables and enabling future growth. Cable fill rates are based on the cross-sectional area of the cables and the inside cross-sectional area of the conduit.

A cable fill percentage of no greater than 50 percent to 60 percent is recommended by industry standards. Cable fill rates are constrained by bends in the pathway where cables must maintain a maximum bend radius and by a maximum height limitation, due to the weight of cables causing possible damage or attenuation. Fiber-optic cables have a maximum height limitation of two inches, and copper cables have a maximum height limitation of six inches.

Larger cabling diameters can decrease the number of cables permitted in a pathway or require larger, more expensive pathways. When selecting cabling for the data center, smaller diameter solutions can go a long way toward saving pathway space and money.

Space within cabinets varies based on the type of cabinet and equipment being installed. Network equipment takes up the majority of horizontal space within the cabinet, which is why ensuring additional available space is important when choosing cabinet models for the data center.

Cabinet depth should provide at least six inches of available recess at the front of the cabinet for fiber and eight inches for copper. As density increases, the cabinets should also provide ample room for additional cable routing so as not to impede airflow throughout the cabinet.

Several installation practices can help manage density and minimize maintenance in the data center. One is to deploy a centralized distribution system in a cross-connect scenario, where all cables are brought to one area for maintenance, patching and servicing. With direct cabling, reconfiguring network elements can require pulling up raised floor tiles and finding additional pathway space. A centralized distribution method, however, enables connecting equipment by using patch cords or jumpers at the cross-connect, while the network elements use permanent equipment cables that remain terminated and are never handled again.

Another benefit of centralized distribution is better utilization of the existing floor space. Even with high-density equipment solutions that make better use of rack space, direct cabling methods can require more cables over time, which, in turn, uses more pathway space in the cabinet.

IT managers and technicians may find that they cannot fill empty cabinet space with new equipment due to cable congestion. Following are the key advantages provided by a centralized distribution system using a cross-connect scenario:

Lower operating costs. Compared to other installation approaches, cross-connect reduces the time needed for adds, moves or changes, providing faster service availability.

Improved reliability and availability. Network reconfigurations take place at the cross-connect without disrupting service or having to handle sensitive equipment connections.