Special Focus: Cabling Infrastructure
Manage Data Center Density
Proper planning and best installation
practices are important for efficiency and
growth.
by Kamlesh Patel
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.
Being able to quickly and easily
access high-density cables and
connectors saves a significant amount of
time, which directly impacts operation
costs.
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.
Reduced downtime. A cross-connect system
enables rapid changes to the network and
reduces risk of downtime, with the ability
to isolate network segments for
troubleshooting and quickly reroute cables
in a disaster-recovery situation.
Network equipment only performs as well
as the cables and connections—a gigabit port
in the data center is of no value if the
cable or connection for that port is
damaged. The key to selecting strategic
solutions for managing data center density
is to ensure that proper bend radius and
physical protection are maintained, cable
routing paths are well defined, and room is
available to access connectors and cables
without affecting adjacent ports.
Pathways and cable-management accessories
should maintain a minimum bend radius of
four times the cable diameter for copper
cable. At turns in fiber runs, a minimum
1.5-inch bend radius is needed, or the bend
radius should be no less than 10 times the
fiber cable's outer diameter. Bends with
less than the specified minimum bend radius
are more likely to fail over time.
PROTECTING FIBER AND COPPER
One strategic solution is reduced
bend-radius fiber, which can be bent to 15
mm (0.590 inch) bend radius. This new fiber,
however, does not eliminate the need for
proper cable-management solutions that also
ensure protection and accessibility.
Pathway trough systems are available that
keep UTP and coaxial cable separated from
fiber, maintain support and bend radius, and
allow additional cables to be added in the
future. Without proper pathway systems,
cables may hang unprotected and accidentally
snag.
Flexible pathway trough systems for
overhead and under-floor cabling also offer
intuitive cable routing that promotes neat,
easily accessible runs as cable traverses
between functional areas and cabinets in the
data center. This ensures easier tracing for
reduced maintenance time.
Common and ample vertical and horizontal
cable-management accessories installed both
within and between racks and cabinets can
help manage data center density and provide
for orderly growth. For example, management
systems that store slack and eliminate the
need for horizontal cable managers can save
on valuable rack space, while also offering
better manageability and organization of
cables.
Another key element in managing data
center density is accessibility. Being able
to quickly and easily access high-density
cables and connectors saves a significant
amount of time, which directly impacts
operation costs. In addition, any cable or
connector should be accessible without
damaging adjacent cables or connectors.
When selecting fiber-optic components,
look for solutions that promote access to
individual adapters and connectors without
affecting adjacent circuits. This can reduce
the time required for upgrades and
maintenance.
For example, angled patch panels and
cable managers enable easy connector access
while reducing cable strain and offering
bend-radius protection. Components that
offer rear access can also make field
termination or splicing fast and efficient,
while also providing a high-density
termination/splice solution for maximizing
rack space.
Finally, companies depend heavily on
their data centers and cannot tolerate
downtime. The solutions chosen should
consistently support the flow of data
without errors that cause retransmission and
delays. As networks expand and bandwidth
demands increase, the data center components
should also support anticipated migration to
higher network speeds without sacrificing
performance.
Managing density is more than just the
equipment that is installed. It is a
comprehensive strategy that includes proper
planning, best installation practices, and
strategic solutions that maintain
protection, organization, accessibility and
reliability of high-density cables and
connections.
Kamlesh Patel is vice technical
director, TrueNet Structured Cabling
Systems, for ADC, Minneapolis.
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