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manual abstract
This paper describes proper methods and recommended techniques and products for safe and effective cable management. Introduction The trend in high performance computing (HPC) data centers is to implement high-density systems that make the most of available facility space. Of high importance with HPC systems are reliability and availability—issues that are addressed with the use of redundant components and cabling. These strategies result in highly populated equipment racks with an abundance of power and data cables. As the component density of a rack increases, so does the need to manage associated cables effectively. Mismanaged or unmanaged cables (Figure 1) can result in several types of issues: • Reduced performance due to signal crosstalk and interference across adjacent cables • Difficult maintenance because components are blocked by cables • Hazardous situations of damaged cables due to unchecked or unprotected movement • Thermal (cooling) issues due to poor or restricted airflow around active components Any of the above situations can require unscheduled downtime to correct, and for enterprise HPC systems that is very costly and unacceptable. Effective management of power and data cabling of a rack can help achieve important overall goals of the IT infrastructure: • Stable, reliable performance through reduced or eliminated crosstalk and interference • Ease of serviceability and maintenance through better and safer access to individual components • Thermal efficiency through maximum air flow for cost-efficient equipment cooling The following sections describe cabling management guidelines that can help achieve the goals of system design. HP solutions that address the cabling issues are also described. Figure 1. Examples of poor cable management in racks Cable routing guidelines To minimize maintenance, safety, and performance issues, routing of power and data cables should be in accordance with the following guidelines. Separation of power and data cables Cables in close proximity to each other, especially those oriented in parallel or in loops, can create electromagnetic interference (EMI) through induction. EMI can result in erratic or error-prone data transfers. To minimize the effects of EMI, power cables should be segregated from data cables as much as possible: • Dress all signal cables on the left side of the rack and all power cables on the right side of the rack. • Arrange and secure excess power and data cabling separately. • Use HP cable management kits described later in this paper to facilitate the segregation. Retention of excess cable Installing a number of components in a rack typically results in the use of some cables that are longer than necessary. This is especially true when similar or redundant components with the same cable types are installed at various levels in a rack. The excess cable lengths are often hurriedly bundled and tied, resulting in problems associated with EMI or in damaged cables. Here are some preferred methods of handling excess cables: • Run and attach excess cables for easy, safe maintenance activities and proper operations. • Ensure that secured cables are not pinched, damaged, or kinked (refer to the “Cable bend radius restrictions” section of this paper). • When possible, use all cable management arms included in component kits. • Use HP cable management kits described later in this paper for maintaining and managing cables. Protection of cables Cables must be protected at points where they might rub or come in contact with sharp edges or heated areas. Extra care must be used with power cables because damaged conductors could cause downtime and because exposed conductors are a safety hazard. To protect cables, HP recommends the following practices: • Avoid dressing cables tightly over sharp edges of railing or panels. • Avoid pinching of cables between components or mounting/sliding rails. • Protect the cables if they may be pinched or damaged. Securing cables and connectors Cables and connectors should be secured to prevent excessive movement and to provide strain relief at critical points. Securing data cables For securing data cables, HP recommends the following practices: • Ensure that cable connections are not stressed from any cable or chassis movement. • Dress cables on management arms securely enough to prevent interference with movement or pinched cables, yet not so tight as to cause binding to the arm. Securing power cables and connectors Power cables and connectors should receive extra care during installation, since loose cables or connectors can result in loss of power and unscheduled downtime. A loose power connector can create high contact resistance that can result in arcing and a fire hazard. HP power distribution products are often supplied with cable retaining clips or clamps (Figure 2), and HP strongly advises using these accessories when they are provided. For securing power cables and connectors, HP recommends the following: • Alway...