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Hardware Today: Caring for Your Cables

Monday Mar 21st 2005 by Drew Robb

Cable management may seem mundane, but it is a vital for a data center to run smoothly. We offer some tips to bring order to the chaos.

Cable management is like the oft-ignored stepchild of server room management — everybody has loads of cables but finding the time to pay them the attention they deserve is another matter. If you don't want that tangle of wires to come back and trip you up, now might be the time to bring some order into the chaos.

According to Brad Wittenkeller, global marketing manager at wiring and communications vendor Panduit, a wide range of errors are being made in data centers around the country.

"Some of the biggest mistakes include poor planning for upgrading/scalability, and disregard for bend radius control of cabling and the impact on network performance," said Wittenkeller. "Consideration also needs to be given to cable routing in high port-density applications, to the amount of space consumed by cabling, and to its impact on air flow."

Cable management begins with racks and cabinets, which should provide ample vertical and horizontal cable management. Far from being merely aesthetically pleasing, well-organized cabling helps keep equipment cool by removing obstacles to air movement.

"Power and data cables can obstruct airflow causing damage to IT equipment that isn't properly cooled," said Russell Senesac, director of InfraStruXure Systems at power and cooling specialist APC.

The formula for Category 6 UTP cable, the most widely used type of network cabling, is to multiply the number of cables by the cable diameter (0.0625 square inches) by 1.30 (to prevent the space for cabling from being more than 70 percent full).

There is an equation that can be used to ensure that any rack or cabinet provides adequate cable management capacity. The formula for Category 6 unshielded twisted pair (UTP) cable, the most widely used type of network cabling, is to multiply the number of cables by the cable diameter (0.0625 square inches) by 1.30 (to prevent the space for cabling from being more than 70 percent full). For 350 cables, that equates to 28.44 square inches for the cable manager.

"Too often, companies place empty racks close together [and] give no thought at all to cabling and then quickly run out of space," said John Schmidt, manager of Ethernet infrastructure at ADC, a vendor specializing in cable management and data center layout. "It is advisable to plan upfront so you have enough room for all the cabling you need at each side of the rack."

ADC recommends cabling systems use common rack frames to simplify rack assembly and provide unified cable management. The company also recommends installing ample vertical and horizontal cable management within and between rack frames. The company further believes it is important to install both overhead and under-floor cable pathways to provide for orderly growth — under-floor pathways for permanent cabling and overhead for temporary cabling.

Not all vendors agree on best practices for the data center, however. Senasac of APC isn't keen on under-floor cabling. The company prefers data and power cables be routed above the rack for easy identification and servicability.

A good model for data center layout, which includes some of the basics of cable management noted above, is covered in standards developed by the Telecommunications Industry Association (TIA). TIA 942 is a standard for network cabling infrastructure in data centers, while TIA 606 identifies key network components.

"TIA 606-compliant labeling improves the management and traceability and reduces total cost of ownership," said Wittenkeller. "And don't forget about proper grounding of racks and active equipment."

Another tip concerns the best way to connect cabling. There are three methods of connecting equipment in the data center: direct connect, interconnect, and cross-connect. Many IT departments get lazy and stick with what appears to be the simplest option — direct connection. However, this is not a wise choice, as it means operators must hunt for cables with every change and pull them to the new location. With interconnection via a patch panel, the IS department need only reroute end cables when changes are made. While this is far more efficient than the direct connection, it is not as easy or reliable as the cross-connection method.

A centralized cross-connect patching system gives all network elements permanent equipment cable connections that are terminated once and never handled again. All changes are made using semi-permanent patch cord connections on the front of the cross-connect system, such as the ADC Ethernet Distribution Frame. This approach reduces the time it takes for adding cards, moving circuits, upgrading software, and performing maintenance. Instead of carrying out moves, additions, and changes on the backplanes of sensitive routing and switching equipment, they are done on the patching field. This lowers costs, speeds up network changes, and improves reliability.

>> A Fiber-Rich Diet

Adding Fiber to the Data Center Diet

Whether due to unfamiliarity or lack of foresight, data center personnel often underestimate their requirements for fiber-optic (FO) cabling. Once FO makes an appearance, after all, the first few strands are rarely the end of it. Therefore, it's best to assume fiber requirements will grow and put a plan in place to efficiently handle that growth.

It is also important to realize fiber is more delicate than other types of wiring. Fiber breaks when it is bent beyond the manufacturer-specified bend diameter. To prevent this, UTP and coaxial cable should be separated from fiber in horizontal pathways to avoid crushing fiber (i.e., electrical cables in cable trays and fiber in troughs mounted on trays).

"Copper tends to crush or kink FO, decreasing bandwidth or even causing total loss of signal," said Schmidt. "This can be avoided by using raised cabling with good separation between copper and FO."

Other best practices for FO include the wise selection of routing paths to reduce the twisting of fibers, allowing for enough access to cabling so that it can be installed or removed without inducing excessive bends in adjacent fiber, and some means of physical fiber protection to minimize the chances accidental damage by technicians and nearby equipment.

Help Wanted

In some cases, it may be wise to bring in a third party to assist in cable management. Companies such as ADC and APC offer best practice guides, white papers, and on-site help with cabling and data center layout. A wide range of vendor tools are also available to manage wiring more efficiently.

Systimax Solutions offers copper, fiber, and high-performance cabling products ranging from 10 M/bs to 10 G/bs, patching tools, and a line of rack and cabinets. Its iPatch intelligent patching system and VisiPatch reverse patching system offer an alternative to traditional patching. The company just released the Systimax 10 Gigabit Ethernet over copper/UTP cabling solution. Sun Microsystems, for example, is installing it at an operational hub in the United Kingdom.

Panduit has a large catalog of cable ties, identification, protection, and routing goods. Its Patented Angled Patch panels and PatchRunner vertical cable managers provide integrated bend radius control solution for patching and high density. The company also sells a TIA 606-compliant labeling solution to properly identify key network components. Proper bend radius can be assured through the Panduit Fiber Runner.

APC and ADC have extensive product portfolios. APC focuses in power production, rack systems, and cooling. It also offers an impressive range of cabling and networking tools. ADC supplies network equipment, software, and integration services for networks that deliver data, video, and voice communications. ADC's Copper 10 is a recent addition, a Category 6 structured cabling system with the necessary characteristics to enable 10 Gb Ethernet transmission over 100 meters. You can use it now for lower bandwidth operations, but it will also operate at 10 Gb when the industry moves to that standard in the near future. ADC's Fiber Guide is also useful for keeping FO and copper separate, and the ADC Ethernet Distribution Frame is a useful cross-connect system.

Thinking Ahead

Most vendors are united in their stress on 10 Gb wiring.

"For those high-speed connections like switch to switch or server to storage it's time to consider 10 Gigabit Ethernet transmission speed over either copper of fiber media," said Mike Barnick, senior manager for solutions marketing with Systimax Solutions.

"Deploy future proof cabling, such as 10 Gig fiber and copper cabling systems, that delivers interoperability and scalability, for organizations with growing bandwidth needs," Wittenkeller advises.

ADC's Schmidt reinforces this message with a cost-comparison of cable material to the labor cost involved in installation.

"As the material itself is not that expensive, pulling the cabling is by far the most important cost," said Schmidt. "Nothing is cheaper than a paid for infrastructure."

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