Cable management for rack-mounted systems
technology brief, 2nd edition
Retention of excess cable.................................................................................................................. 3
Protection of cables.......................................................................................................................... 3
Securing power cables and connectors........................................................................................... 4
Thermal issues with cable routing....................................................................................................... 5
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.
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.
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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:
• Always use any provided hardware (such as retaining clips or tie strips) to secure power connectors
and cords to the product chassis.
• When possible, secure PDU power cables with removable ties to prevent accidental removal of the
cords from the system.
Figure 2. Example of retaining, clamp system securing power cords on HP products
Cable bend-radius restrictions
Routing cables typically requires looping excess cable or bending cable around chassis components.
The bend radius is defined as the minimum radius (Figure 3) to which a cable may safely be bent
without damaging the cable or affecting its performance.
Figure 3. Cable bend radius
Cable
0°
R2 (bend radius away
from connector)
R1 (bend radius at connector)
R1
R2
90°
Radius (R)
To avoid the consequences of a too short or too tight bend radius, HP recommends the following
practices:
• Avoid tight bend radii. Never bend cables tight enough to cause a crease in the sheathing.
• With no exceptions, fiber cables must not violate their minimum bend radius.
• Avoid excessive bends in cable, and run as large a bend as space allows.
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• Use cable routing accessories designed to maintain and secure cable.
• Leave enough slack in cables for operation of articulated arms and rail slides.
Since actual conductor size and type vary among types of cables, the bend radius rule can differ
among cable types. For example, Table 1 lists the minimum bend radius for HP fiber optic cables and
HP InfiniBand cables.
Table 1. Bend radius for HP cables
Cable type
Minimum bend radius (R, R1, or R2)
HP LC-Type fiber optic
HP SC-Type fiber optic
R = 0.8in (~2cm)
R =1in (~3cm)
R1 = 4.6in (12cm)
R2 = 2.3in (6cm)
HP InfiniBand 4xcable
Note
The bend radius restrictions on some cable types, such as
InfiniBand cable, vary depending upon connector proximity.
For other cables, HP recommends that users refer to cable
specifications or contact the cable supplier for more
information.
Excessive bending of cables can create one or more of the following problems:
• For power cables, stressed insulators or arcing across conductors
• For copper data cables, stressed terminators, stress on center conductors, or disturbed twists on
conductors that increase sensitivity to noise
• For fiber optic cables, micro-bending of fibers that results in degradation of light transmission or
breaking of fibers, which results in loss of signal
Thermal issues with cable routing
HP rack-mountable products that use forced-air cooling typically draw cool air through the front of the
chassis and push warm air out the back. If this air flow is restricted in any way, component
temperatures can rise, resulting in unscheduled system downtime due to thermal shutdown or damage.
For safe and reliable operation, ventilation slots and blowers at the rear of products must not be
obstructed by any components, including cables. Therefore, for proper cooling of rack-mounted
components, ensure that cabling does not impede the airflow to or from the rack-mountable servers.
Routing fiber optic cable
Fiber optic cable is lighter than copper cable; but it is relatively delicate, must be handled carefully
during installation, and may require extra protection. Damaged fiber optic cable poses no safety
hazards but can result in degraded or interrupted performance. HP recommends the following
guidelines for installing fiber optic cable:
• Use only Velcro ties to reduce the chance of damaging cable from over-cinching or accidental
cutting.
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• Do not allow other cables or components to exert tension on fiber optic cables, which can be easily
crushed or damaged.
• Avoid routing fiber optic cable around chassis and cabinet corners. If this is unavoidable, protect
the cable.
Routing network cable
Network interconnects can involve a large amount of cabling due to the component/data path
redundancy required to meet high availability goals. Network devices also require high serviceability,
so cabling must be arranged to allow easy access to individual circuits.
HP recommends the following guidelines for routing data cables:
• For components that must be movable while powered on, ensure that a full range of motion is
possible without cable interference or disconnection.
• When securing cables inside the rack, dress the bundle in a way that avoids interference with
installed components, rack side panels, or rails.
• Do not block access to field-replaceable components.
HP Cable Management Kit
HP offers a complete line of products that provide reliable, serviceable, and safe cabling options for
assembling rack installations. Routing, securing, and protection solutions available from HP are listed
in Table 2 and can be found at the main rack options product page at
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Table 2. HP cabling solutions
Product
HP part number
Description
Cable Management
D-ring Kit
This kit contains 10 D-rings that mount in the back rails
of the rack and allow for cables to be routed and
organized within the rack.
168233-B21
Network Cable
Management Kit
This kit provides an easy way to organize and route
cables within HP racks. Cable clips, cable rings, and
1U and 2U access panels are included.
AF099A
Hook and Loop
Strips
Adjustable, reusable strap with metal clip that can
attach to rack perforations or other clips.
379820-B21
383982-B21
(600mmWide)
Designed to mount on top of the HP Rack 10000
Series for orderly and efficient cable routing. The three
levels within the trays allow for routing power, data,
and fibre channel cables separately.
Rack-Top Cable Tray
383983-B21
(800mm wide)
Rack-to-Rack
Adjustable cable bridge used to transfer cables from
the back of a rack, across the datacenter hot aisle, to
the back of another rack. Comes in a single size.
Adjustable Cable
Tray, Aisle Transfer
Bridge
383984-B21
HP Factory Express services
than 50 services. Through Factory Express, HP offers routing and cabling management service in
accordance with the best cabling practices.
1 HP Factory Express is a robust portfolio of flexible, pre-priced, configured, customized, and integrated factory
solutions and deployment services. Through Factory Express, HP racks can be customized, configured, and
integrated into ready-to-deploy solutions to save customers time, money, and resources.
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For more information
For additional information about racks, rack options, and accessories, refer to the HP Infrastructure
To learn more about HP Factory Express, contact your HP sales representative or visit our website at
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© 2007 Hewlett-Packard Development Company, L.P. The information contained herein is
subject to change without notice. The only warranties for HP products and services are set forth
in the express warranty statements accompanying such products and services. Nothing herein
should be construed as constituting an additional warranty. HP shall not be liable for technical
or editorial errors or omissions contained herein..
TC071203TB, December 2007
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