Fundamental Cabling Strategies for Data Centers
Transcript
Slide 1
Welcome to Fundamental Cabling Strategies for Data Centers.
Slide 2
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Slide 3
At the completion of this course, you will be able to:
•
Discuss the evolution of cabling
•
Classify different types of common data center cables
•
Describe cabling installation practices
•
Identify the strategies for selecting cabling topologies
•
Utilize cable management techniques
•
Recognize the challenges associated with cabling in the data center
Slide 4
From a cost perspective, building and operating a data center represents a significant piece of any
Information Technology (IT) budget. The key to the success of any data center is the proper design and
implementation of core critical infrastructure components. Cabling infrastructure, in particular, is an
important area to consider when designing and managing any data center.
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The cabling infrastructure encompasses all data cables that are part of the data center, as well as all of the
power cables necessary to ensure power to all of the loads. It is important to note that cable trays and cable
management devices are critical to the support of IT infrastructure as they help to reduce the likelihood of
downtime due to human error and overheating.
Slide 5
This course will address the basics of cabling infrastructure and will discuss cabling installation practices,
cable management strategies and cable maintenance practices. We will take an in-depth look at both data
cabling and power cabling. Let’s begin with a look at the evolution of data center cabling.
Slide 6
Ethernet protocol has been a data communications standard for many years. Along with Ethernet, several
traditional data cabling practices continue to shape how data cables are deployed.
•
High speed data cabling over copper is a cabling medium of choice
•
Cable fed into patch panels and wall plates is common
•
The RJ45 is the data cable connector of choice
The functionality within the data cables and associated hardware, however, has undergone dramatic change.
Increased data speeds have forced many physical changes. Every time a new, faster standard is ratified by
standardization bodies, the cable and supporting hardware have been redesigned to support it. New test
tools and procedures also follow each new change in speed. These changes have primarily all been
required by the newer, faster versions of Ethernet, which are driven by customers’ needs of more speed and
bandwidth. When discussing this, it is important to note the uses and differences of both fiber-optic cable,
and traditional copper cable. Let’s compare these two.
Slide 7
Copper cabling has been used for decades in office buildings, data centers and other installations to provide
connectivity. Copper is a reliable medium for transmitting information over shorter distances; but its
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performance is only guaranteed up to 109.4 yards (100 meters) between devices. (This would include
structured cabling and patch cords on either end.)
Copper cabling that is used for data network connectivity contains four pairs of wires, which are twisted
along the length of the cable. The twist is crucial to the correct operation of the cable. If the wires unravel,
the cable becomes more susceptible to interference.
Copper cables come in two configurations:
Solid cables provide better performance and are less susceptible to interference making them the
preferred choice for use in a server environment.
Stranded cables are more flexible and less expensive, and typically are only used in patch cord
construction.
Copper cabling, patch cords, and connectors are classified based upon their performance characteristics
and for which applications they are typically used. These ratings, called categories, are spelled out in the
TIA/EIA 568 Commercial Building Telecommunications Writing Standard.
Slide 8
Fiber-optic cable is another common medium for providing connectivity. Fiber cable consists of five
elements. The center portion of the cable, known as the core, is a hair thin strand of glass capable of
carrying light. This core is surrounded by a thin layer of slightly purer glass, called cladding, that contains
and refracts that light. Core and cladding glass are covered in a coating of plastic to protect them from dust
or scratches. Strengthening fibers are then added to protect the core during installation. Finally, all of these
materials are wrapped in plastic or other protective substance that serves as the cable’s jacket.
A light source, blinking billions of times per second, is used to transmit data along a fiber cable. Fiber-optic
components work by turning electronic signals into light signals and vice versa. Light travels down the
interior of the glass, refracting off of the cladding and continuing onward until it arrives at the other end of
the cable and is seen by receiving equipment.
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When light passes from one transparent medium to another, like from air to water, or in this case, from the
glass core to the cladding material, the light bends. A fiber cable’s cladding consists of a different material
from the core — in technical terms, it has a different refraction index — that bends the light back toward the
core. This phenomenon, known as total internal reflection, keeps the light moving along a fiber-optic cable
for great distances, even if that cable is curved. Without the cladding, light would leak out.
Fiber cabling can handle connections over a much greater distance than copper cabling, 50 miles (80.5
kilometers) or more in some configurations. Because light is used to transmit the signal, the upper limits of
how far a signal can travel along a fiber cable is related not only to the properties of the cable but also to the
capabilities and relative location of transmitters.
Slide 9
Besides distance, fiber cabling has several other advantages over copper:
Fiber provides faster connection speeds
Fiber is not prone to electrical interference or vibration
Fiber is thinner and light-weight, so more cabling can fit into the same size bundle or limited spaces
Signal loss over distance is less along optical fiber than copper wire
Two varieties of fiber cable are available in the marketplace: multimode fiber and single mode fiber.
Multimode is commonly used to provide connectivity over moderate distances, such as those in most data
center environments, or among rooms within a single building. Single mode fiber is used for the longest
distances, such as among buildings on a large campus, or between sites.
Copper is generally the less expensive cabling solution over shorter distances (i.e. the length of data center
server rows), while fiber is less expensive for longer distances (i.e. connections among buildings on a
campus).
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Slide 10
In the case of data center power cabling, however, historical changes have taken a different route.
In traditional data centers, designers and engineers were not too concerned with single points of failure.
Scheduled downtime was an accepted practice. Systems were periodically taken down to perform
maintenance, and to make changes. Data center operators would also perform infrared scans on power
cable connections prior to the shutdowns to determine problem areas. They would then locate the hot spots
that could indicate possible risk of short circuits and address them.
Traditional data centers, very often, had large transformers that would feed large uninterruptible power
supplies (UPSs) and distribution switchboards. From there, the cables would go to distribution panels that
would often be located on the columns or walls of the data center. Large UPSs, transformers, and
distribution switchgear were all located in the back room.
The incoming power was then stepped down to the correct voltage and distributed to the panels mounted in
the columns. Cables connected to loads, like mainframe computers, would be directly hardwired to the
hardware. In smaller server environments, the power cables would be routed to power strips underneath the
raised floor. The individual pieces of equipment would then plug into those power strips, using sleeve and
pin connectors, to keep the cords from coming apart.
Slide 11
Downtime is not as accepted as it once was in the data center. In many instances, it is no longer possible to
shut down equipment to perform maintenance. A fundamentally different philosophical approach is at work.
Instead of the large transformers of yesterday, smaller ones, called power distribution units (PDUs) are now
the norm. These PDUs have moved out of the back room, onto the raised floor, and in some cases, are
integrated into the racks. These PDUs feed the critical equipment. This change was the first step in a new
way of thinking, a trend that involved getting away from the large transformer and switchboard panel.
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Modern data centers also have dual cord environments. Dual cord helps to minimize a single point of failure
scenario. One of the benefits of the dual cord method is that data center operators can perform
maintenance work on source A, while source B maintains the load. The server never has to be taken offline
while upstream maintenance is being performed.
This trend began approximately 10 years ago and it was clearly driven by the user. It became crucial for
data center managers to maintain operations 24 hours a day, 7 days per week. Some of the first businesses
to require such operations were the banks, who introduced ATMs, which demanded constant uptime. The
customer said “We can no longer tolerate a shutdown”.
Now that we have painted a clear picture of the history of cabling infrastructure, we’ll discuss the concept of
modularity and its importance in the data center.
Slide 12
Modularity is an important concept in the contemporary data center. Modular, scalable Network Critical
Physical Infrastructure (NCPI) components have been shown to be more efficient and more cost effective.
The data cabling industry tackled the issue of modularity decades ago. Before the patch panel was
designed, many adds, moves and changes were made by simply running new cable. After years of this ‘run
a new cable’ mentality, wiring closets and ceilings were loaded with unused data cables. Many wiring
closets became cluttered and congested. The strain on ceilings and roofs from the weight of unused data
cables became a potential hazard. The congestion of data cables under the raised floor also impeded
proper cooling and exponentially increased the potential for human error and downtime.
Slide 13
In the realm of data cabling, the introduction of the patch panel brought an end to the ‘run a new cable’
philosophy and introduced modularity to network cabling. The patch panel, located either on the data center
floor or in a wiring closet, is the demarcation point where end points of bulk cable converge. If a data center
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manager were to trace a data cable from end to end, starting at the patch panel, he would probably find
himself ending at the wall plate. This span is known as the backbone.
The modularity of the system is in the use of patch cables. The user plugs his patch cable into a wall plate. If
he needs to move a computer, for example, he simply unplugs his patch cable and connects into a different
wall plate. The same is true on the other end, back at the patch panels. If a port on a hub or router
malfunctions, the network administrator can simply unplug it and connect it into another open port.
Data center backbone cabling is typically designed to be non-scalable. The data cabling backbone, 90% of
the time, is located behind the walls, not out in the open.
Typically a network backbone, when installed, especially in new construction scenarios, accounts for future
growth considerations. Adds, moves and changes can be very costly once the walls are constructed. In new
construction it is best to wire as much of the building as possible, with the latest cable standard. This
reduces expenses once the walls are constructed.
Now that we have discussed the concept of modularity, let’s overview the different types of data cables that
exist in a data center.
Slide 14
So, what are the different types of common data center specific data cables?
Category 5 (Cat 5) was originally designed for use with 100 Base-T. Cat 5e supports 1 Gig Ethernet. Cat 6a
supports 10 Gig Ethernet. It is important to note that a higher rated cable can be used to support slower
speeds, but the reverse is not true. For example, a Cat 5e installation will not support 10 Gig Ethernet, but
Cat 6a cabling will support 100 Base-T.
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Cable assemblies can be defined as a length of bulk cable with a connector terminated onto both ends.
Many of the assemblies used are patch cables of various lengths that match or exceed the cabling standard
of the backbone. A Cat 5e backbone requires Cat 5e or better patch cables.
Slide 15
Data center equipment can require both standard and custom cables. Some cables are specific to the
equipment manufacturer. One example of a common connection would involve a scenario in which a Cisco
router with the 60-pin LFH connector connected to a router with V.35 interface requires an LFH60 to V.35
Male DTE cable.
An example of a less common connection would be a stand alone tape backup that may have a SCSI
interface. If the cable that came with the equipment does not match up to the SCSI card in a computer, the
data center manager will find himself looking for a custom SCSI cable.
A typical example of the diversity of cables required in the data center is a high speed serial router cable. In
a wide area network (WAN), routers are typically connected to modems, which are called DSU/CSU’s.
Some router manufacturers feature unorthodox connectors on their routers. Depending on the interface that
the router and DSU/CSU use to communicate to one another, several connector possibilities exist.
Other devices used in a computer room can require any one of a myriad of cables. Common devices
besides the networking hardware are telco equipment, KVM’s, mass storage, monitors, keyboard and
mouse, and terminal servers. Sometimes brand-name cables are expensive or unavailable. A large market
of manufacturer equivalent cables exists, from which the data center manager can choose.
Slide 16
When discussing data center power cabling, it is important to note that American Wire Gauge (AWG) copper
wire is the common medium for transporting power in the data center. This has been the case for many
years and it still holds true in modern data centers.
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The formula for power is Amp x Volts = Power; and data center power cables are delineated by amperage.
The more power that needs to be delivered to the load, the higher the amperage has to be. (Note: The
voltage will not be high under the raised floor. It will be less than 480V; most servers are designed to handle
120 or 208V.)
If the level of power is the same, the amperage and voltage are the same. As the amperage increases or
decreases, the gauge of the wire needs to be larger or smaller to accommodate the change in amperage.
AWG ratings organize copper wire into numerous recognizable and standard configurations.
A relatively new trend in the domain of data center power cabling is the invention of the whip. Whips are preconfigured cables with a twist lock cap on one end and insulated copper on the other end. The insulated
copper end feeds a breaker in the main PDU; the twist lock end feeds the rack mounted PDU that supplies
the intelligent power strips in the rack. Server equipment then plugs directly into the power strip. With whips,
there is no need for wiring underneath the floor (with the possible exception of the feed to the main PDU
breakers). Thus, the expense of a raised floor can be avoided. Another benefit of whips is that a licensed
electrician is not required to plug in the twist lock connectors of the whip into the power strip twist lock
receptacles.
Slide 17
Dual cord, dual power supply also introduced significant changes to the data center power cabling scheme.
In traditional data centers, computers had one feed from one transformer or panel board, and the earliest
PDUs still only had one feed to servers. Large mainframes required two feeds to keep systems consistently
available. Sometimes two different utilities were feeding power to the building.
Now, many servers are configured to support two power feeds, hence the dual cord power supply. Because
data center managers can now switch from one power source to another, this allows for maintenance on
infrastructure equipment without having to take servers offline.
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It is important to understand that the power cabling requirements to support the dual cord power supply
configuration have doubled as a result. The same wire, the same copper, and the same sizes, are required
as was required in the past, but now data center designers need to account for double the power
infrastructure cable, including power related infrastructure that may be located in the equipment room that
supports the data center.
Now that we’ve talked about a basic overview of both power and data cabling, let’s take a look at some best
practices for cabling in the data center.
Slide 18
Some best practices for data cabling include:
•
Overhead deployments
o
Overhead cables that are in large bundles should run in cable trays or troughs. If the
manufacturer of the tray or trough offers devices that keep the cable bend radius in check then
they should be used as well. Do not over tighten tie wraps or other hanging devices. It can
interfere with the performance of the cable.
•
Underfoot deployments
o
Be cognizant of the cable’s bend radius specifications and adhere tightly to them. Do not over
tighten tie wraps. This can interfere with the performance of the cable.
•
Rack installations
o
As talked about previously, be cognizant of the cable’s bend radius specifications and adhere
tightly to them. Don’t over tighten tie wraps. This can interfere with the performance of the
cable. Use vertical and/or horizontal cable management to take up any extra slack.
•
Testing cables
o
There are several manufacturers of test equipment designed specifically to test today’s high
speed networks. Make sure that the installer tests and certifies every link. A data center
manager can request a report that shows the test results.
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Are there any common practices that should be avoided? When designing and installing the network’s
backbone care should be taken to route all Unshielded Twisted Pair (UTP is the U.S. standard) or Shielded
Twisted Pair (STP is the European standard) cables away from possible sources of interference such as
power lines, electric motors or overhead lighting.
Slide 19
Power cabling best practices are described in the National Electric Code (NEC).
When addressing best practices in power cabling, it is important that data center professionals use the term,
“continuous load’. The continuous load is defined as any load left on for more than 3 hours, which is, in
effect, all equipment in a data center. Due to the requirements of the continuous load, data center operators
are forced to take all rules that apply to amperages and wire sizes and de-rate those figures by 20%. For
example, if a wire is rated for 100 amps, the best practice is not to run more than 80 amps through it. Let’s
discuss this further.
Over time, cables can get overheated. The de-rating approach helps avoid overheated wires that can lead
to shorts and fires. If the quantity of copper in the cable is insufficient for the amperages required, it will heat
to the point of melting the insulation. If insulation fails, the copper is exposed to anything metal or grounded
in its proximity. If it gets close enough, the electricity will jump or arc and could cause a fire to start.
Undersized power cables also stress the connections. If any connection is loose, the excess load
exacerbates the situation. The de-rating of the power cables takes these facts into account.
To further illustrate this example, let’s compare electricity to water. If too much water gets pushed into a pipe,
the force of the water will break the pipe if it is too small. Amperages are forcing electricity through the wire;
therefore, the wire is going to heat up if the wire is undersized.
The manufacturer, or supplier, of the cable provides the information regarding the circular mill, or the area of
the wires, inside the cable. The circular mill does not take into account the wire insulation. The circular mill
determines how much amperage can pass through that piece of copper.
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Next, let’s compare overhead and under the floor installations.
Slide 20
The benefit of under the floor cabling is that the cable is not visible. Many changes can be made and the
wiring will not be seen. The disadvantage of under the floor cabling is the significant expense of constructing
a raised floor. Data center designers also need to take into account the danger of opening up a raised floor
and exposing other critical systems like the cooling air flow system, if the raised floor is used as a plenum.
With overhead cabling, data center designers can use cabling trays to guide the cables to the equipment.
They can also run conduit from the PDU directly to the equipment or computer load. The conduit is not
flexible, however, which is not good if constant change is expected.
A best practice is to use overhead cables which are all pre-configured in the factory and placed in the
troughs to the equipment. This standardization creates a more convenient, flexible environment for the data
center of today.
Slide 21
Where your power source is, where the load is, and what the grid is like, all affect the design and layout of
the cabling in the data center. When discussing overhead cabling, data centers designers are tasked with
figuring out the proper placement of cables ahead of time. Then, they can decide if it would be best to have
the troughs directly over the equipment or in the aisle. Also designers have to take into account local codes
for distributing power. For example, there are established rules that require that sprinkler heads not be
blocked. If there is a 24 inch (60.96 cm) cable tray, designers could not run that tray any closer than 10
inches (25.4 cm) below the sprinkler head to cover up or obstruct the head. They would need to account for
this upfront in the design stage.
Now that we’ve touched upon best practices for installation, let’s discuss some strategies for selecting
cabling topologies.
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Slide 22
Network Topology deals with the different ways computers (and network enabled peripherals) are arranged
on or connected to a network. The most common network topologies are:
Star. All computers are connected to a central hub.
Ring. Each computer is connected to two others, such that, starting at any one computer, the
connection can be traced through each computer on the ring back to the first.
Bus. All computers are connected to a central cable, normally termed bus or backbone.
Tree. A group of start networks are each connected to a linear backbone.
For data cabling, in IEEE 802.3, UTP/STP Ethernet scenarios, a star network topology is used. Star
topology implies that all computers are connected to a central hub. In it’s simplest form a UTP/STP Ethernet
Star topology has a Hub at the center and devices (i.e. personal computer, printers, etc.) connected directly
to it. Small LANs fit this simple model. Larger installations can be much more complicated, with segments
connecting to other segments, but the basic Star topology remains intact.
Slide 23
Power cables can be laid out either overhead in troughs or below the raised floor. Many factors come into
play when deciding on a power distribution layout from the PDUs to the racks. The size of the data center,
the nature of the equipment being installed and budget are all variables. However, be aware that two
approaches are commonly utilized for distribution of power cables in the data center.
Slide 24
One approach is to run the power cables inside conduits from large wall mounted or floor mounted PDUs to
each cabinet location. This works moderately well for a small server environment with a limited number of
conduits. This does not work well for larger data centers when cabinet locations require multiple power
receptacles.
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Slide 25
Another approach, more manageable for larger server environments, is the installation of electrical
substations at the end of each row in the form of circuit panels. Conduit is run from power distribution units
to the circuit panels and then to a subset of connections to the server cabinets.
This configuration uses shorter electrical conduit, which makes it easier to manage, less expensive to install,
and more resistant to a physical accident in the data center. For example, if a heavy object is dropped
through a raised floor, the damage it can cause is greatly reduced in a room with segmented power,
because fewer conduits overlap one another in a given area.
Even more efficient is to deploy PDUs in the racks themselves and to have whips feed the various racks in
the row.
Slide 26
What are the best practices for cable management and organization techniques? Some end users purchase
stranded bulk data cable and RJ45 connectors and manufacture their own patch cables on sight. While
doing this assures a clean installation with no excess wire, it is time consuming and costly. Most companies
find it more prudent to inventory pre-made patch cables and use horizontal or vertical cable management to
take up any excess cable. Patch cables are readily available in many standard lengths and colors.
Are there any common practices that should be avoided? All of today’s high speed networks have minimum
bend radius specifications for the bulk cable. This is also true for the patch cables. Care should be taken not
to exceed bend radius on the patch cables.
Slide 27
Proper labeling of power cables in the data center is a recommended best practice. A typical electrical panel
labeling scheme is based on a split bus (two buses in the panel) where the labels represent an odd
numbered side and an even numbered side. Instead of normal sequenced numbering, the breakers would
be numbered 1, 3, 5 on the left hand side and would be numbered 2, 4, 6 on the right side, for example.
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When labeling a power cable or whip, the PDU designation from the circuit breaker would be a first identifier.
This identifier number indicates from where the whip comes. Identifying the source of the power cable can
be complicated because the power may not be supplied from the PDU that is physically the closest to the
rack and may not be the one that is feeding the whip. In addition, data center staff may want to access the
“B” power source even though the “A” power source might be physically closer. This is why the power
cables need to be properly labeled at each end. The cable label needs to indicate the source PDU (i.e.
PDU1) and also identify the circuit (i.e. circuit B).
Ideally on the other end of the cable, a label will indicate what load the cable is feeding (i.e. SAN device, or
Processer D23). To help clarify labeling, very large data centers are laid out in two foot squares that match
the raised floor. They are usually addressed with east/west and numbered designations. For example, “2
west by 30 east” identifies the location of an exact square on the data center floor (which is supporting a
particular piece or pieces of equipment). Therefore the label identifies the load that is being supported by
the cable. Labeling of both ends of the cable in an organized, consistent manner allows data center
personnel to know the origin of the opposite end.
Slide 28
With network data cabling, once the backbone is installed and tested it should be fairly stable. Infrequently,
a cable may become exposed, damaged, and therefore needs to be repaired or replaced. But once in place,
the backbone of a network should remain secure. Occasionally, patch cables can be jarred and damaged;
this occurs most commonly on the user end.
Since the backbone is fairly stable except for occasional repair, almost all changes are initiated simply by
disconnecting a patch cable and reconnecting it somewhere else. The modularity of a well designed cabling
system allows users to disconnect from one wall plate, connect to another and be back up and running
immediately. In the data center, adds, moves and changes should be as simple as connecting and
disconnecting patch cables.
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So what are some of the challenges associated with cabling in the data center? We’ll talk about three of the
more common challenges.
Slide 29
The first challenge is associated with useful life.
The initial design and cabling choices can determine the useful life of a data cabling plant. One of the most
important decisions to make when designing a network is choosing the medium: copper, fiber or both?
Every few years newer-faster-better copper cables are introduced into the marketplace, but fiber seems to
remain relatively unchanged. If an organization chose to install FDDI grade 62.5/125 fiber 15 years ago, that
organization may still be using the same cable today. Whereas if the same organization had installed Cat 5
the organization more than likely would have had replaced it by now. In the early days few large installations
were done in fiber because of the cost. The fiber was more expensive and so was the hardware that it
plugged into. Now the costs of fiber and copper are much closer. Fiber cabling is also starting to change.
The current state of the art is 50/125 laser optimized for 10 Gig Ethernet.
Next, there is airflow and cooling.
There are a few issues with cables and cabling in the data center that effect airflow and cooling. Cables
inside of an enclosed cabinet need to be managed so that they allow for maximum airflow, which helps
reduce heat. When cooling is provided through a raised floor it is best to keep that space as cable free as
possible. For this reason expect to see more and more cables being run across the tops of cabinets as
opposed to at the bottom or underneath the raised floor.
Finally, there is management and labeling.
Many manufacturers offer labeling products for wall plates, patch panels and cables. Also software
packages exist that help keep track of cable management. In a large installation, these tools can be
invaluable.
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Let’s take a look at some expenses associated with cabling in the data center.
Slide 30
For data cabling, the initial installation of a cabling plant, and the future replacement of that plant, are the
two greatest expenses. Beyond installation and replacement costs, the only other expense is adding patch
cables as the network grows. The cost of patch cables is minimal considering the other costs in an IT
budget. Cabling costs are, for the most part, up front costs.
Regarding power cables, the design of the data center, and the location of the PDUs, will have a significant
impact on costs. Dual cord power supplies are driving up the cost because double the power cabling is
required. Design decisions are critical. Where will the loads be located? How far from the power distribution?
What if PDUs are fed from different circuits? If not planned properly, unnecessarily long power cable runs
will be required and will drive up overall data center infrastructure costs.
Next, let’s look at cabling maintenance.
Slide 31
How are cables replaced?
Patch cables are replaced by simply unplugging both ends and connecting the new one. However, cables
do not normally wear out. Most often, if a cable shorts, it is due to misuse or abuse. Cable assemblies have
a lifetime far beyond the equipment to which they are connected.
How are cables rerouted?
If the cable that needs to be rerouted is a patch cable then it can simply be unplugged on one or both ends
and rerouted. If the cable that needs to be rerouted is one of the backbone cables run through the walls,
ceilings, or in cable troughs, it could be difficult to access. The backbone of a cabling installation should be
worry-free, but if problems come up they can sometimes be difficult to address. It depends on what the
issue is, where it is, and what the best solution is. Sometimes re-running a new link is the best solution.
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Slide 32
The equipment changes quite frequently in the data center; on the average a server changes every 2-3
years. It is important to note that power cabling only fails at the termination points. The maintenance occurs
at the connections. Data center managers need to scan those connections and look for hot spots. It is also
prudent to scan the large PDU and its connection off the bus for hot spots.
Heat indicates that there is either a loose connection or an overload. By doing the infrared scan, data center
operators can sense that failure before it happens. In the dual cord environment, it becomes easy to switch
to the alternate source, unplug the connector, and check it’s connection.
Slide 33
Every few feet, the power cable is labeled with a voltage rating, an amperage rating, and the number of
conductors that can be found inside the cable. This information is stamped on the cable. American Wire
Gauge (AWG) is a rating of the size of the copper, and identifies the number of conductors in the cable.
Inside a whip there are a minimum of 3 wires, one hot, one neutral, and one ground. It is also possible, to
have 5 wires (3 hot, 1 neutral, 1 ground) inside the whip. Feeder cables which feed the Uninterruptible
Power Supply (UPS) and feed the PDU are thicker, heavier cables. Single conductor cables (insulated
cables with multiple strands of uninsulated copper wires inside) are usually placed in groups within metal
conduit to feed power hungry data center infrastructure components such as large UPSs and Computer
Room Air Conditioners (CRACs). Multiple conductor cables, (cables inside the larger insulated cable that
are each separately insulated) are most often found on the load side of the PDU. Single conductors are
most often placed within conduit, while multiple conductor cables are generally distributed outside of the
conduit. Whips are multiple conductor cables.
Slide 34
To summarize, let’s review some of the information that we have covered throughout the course.
A modular, scalable approach to data center cabling is more energy efficient and cost effective
Copper and fiber data cables running over Ethernet networks are considered the standard for data
centers
Fundamental Cabling Strategies for Data Centers
P a g e | 18
© 2013 Schneider Electric. All rights reserved. All trademarks provided are the property of their respective owners.
American Wire Gauge copper cable is a common means of transporting power in the data center
Cabling to support dual cord power supplies helps to minimize single points of failure in a data
center
To minimize cabling costs, it important for data center managers to take a proactive approach to
the design, build, and operation of the data center of today
Slide 35
Thank you for participating in this course.
Fundamental Cabling Strategies for Data Centers
P a g e | 19
© 2013 Schneider Electric. All rights reserved. All trademarks provided are the property of their respective owners.