R&M Data Center Handbook

www.datacenter.rdm.com
3.9 Transmission Media
Although the foundation for the standardization of structured communication
cabling was laid in the 1990s and standards have been continuously deve-loped
to data, the data center and server room area have been neglected during this
entire period. The first ANSI (American National Standards Institute) standard for
data centers, the TIA-942, was published only in 2005, whereupon international
and European standards followed.
The result of this neglect becomes obvious when entering many data centers;
one finds a passive IT infrastructure that is implemented without a solid, needsoriented
design and has become increasingly chaotic over the years. This
chaos is further intensified – in spite of the introduction of VM solutions – by the
increasing number of servers with may have very different requirements for
transmission technology or the type of LAN interface supported.
The time has therefore come to rethink the technologies practiced up to this point as well as the alternative
options available, in both the realization of new data centers as well as redesign of existing ones. The following
section discusses these alternatives, and in the process attempts to describe methods that remain practically
relevant and realistic.
Definition and Specification
Any sensible planning of technical measures must always be preceded by an analysis of requirements. The first
step to that end is to recognize or identify the components that will be subject to these requirements. Obviously,
cabling involves components which make it possible to connect a server to an LAN connection.
In retrospect, one can say that the structured communication cabling approach in accordance with EN 50173 (or
ISO/IEC 11801 or EIA/TIA 568) was successful. This is because this standardization approach ended up introducing
a cabling infrastructure that can be scaled according to needs, and permits a variety of quality grades. It
was only as a result of the specifications in these standards that a stability and security was guaranteed to the
planners and users which led to a high service life of current cabling systems.
Put more simply, the secret to success of the standards implemented in this area consists of two principles, the
specification of cabling components, and the recommendation (not regulation!) for linking these components
together in specific topology variants. A fundamental strength of the favored star-shape topology results from its
scalability, since through the use of different materials every layer of the hierarchy can be scaled irrespective of
the other layers. New supplementary standards that are based on this proven star structure were therefore
developed for data center cabling systems. They take advantage of this strength and are adapted to these
environmental requirements as already described in section 3.1.
The following improvements, among others, are achieved by using standards-compliant cabling systems:
• Distributors are laid out and positioned better, in a way that minimizes patch and device connection cable
lengths and provides optimal redundancies in the cabling system.
• Work areas that are susceptible to faults are limited to the patching area in the network cabinet and in the
server cabinet. If the cables used there are damaged, the cables in the raised floor do not need to be
replaced as well.
• The selection of the modules in the copper patch panel as well as the network cabinet and server cabinet
can be made independently of the usual requirement for RJ45 compatibility. A connection cable can be
used to adapt the plug to any connecting jack for active network components or network interface cards.
A similar level of freedom is also provided by glass fibers. In this case, connectors of the highest
technical quality are to be used in patch panels.
• Inaccessible areas can be continuously documented and labeled.
Now that the reasons for implementing a structured cabling system in a data center have been determined as
above, we will now specify the requirements for materials, especially requirements with regard to data communication.
An fierce debate currently prevails over the question of whether glass fiber or copper should be the first choice for
media in a data center. In the opinion of the author, there is no solid reason for recommending one of these media
types over the other in this area, nor is one strictly necessary in terms of a structured cabling system. However, it
is certainly worthwhile to examine the advantages and disadvantages of both technologies in light of their use in
data centers.
R&M Data Center Handbook V2.0 © 08/2011 Reichle & De-Massari AG Page 109 of 156