When considering the impact of converged infrastructure and hyperconvergence on cabling, it is important to first understand how data center topologies are evolving. Over the past few years, the advent of software-defined networking has driven a shift in data center designs from three-tier to leaf-like topologies.
Data Center Cabling
A three-tier design is where the bottom layer (or access layer) connects hosts to the network. The middle layer is the distribution or aggregation layer. The core layer provides routing services to other parts of the data center as well as services outside the data center space, such as Internet access and connections to other data center locations. An example of this topology is to use Cisco 7000 series as core switches, Cisco series as aggregation switches, and Cisco 2000 series as access switches.
Data Center Cabling
Although this design is simple, it does have some limitations in terms of scalability. If the uplinks between tiers are oversubscribed, bottlenecks can be encountered. This can be due to delays caused by traffic flowing through each layer, as well as blocking redundant links using protocols such as spanning tree.
Leaf topology is another design in which leaf switches form the access layer. These leaf switches are fully meshed with all spine switches. The mesh ensures that each leaf switch has no more than one connection to other leaf switches.
This topology is easy to scale. Links between layers can be routed or switched. All links are forwarding – this means that no links in the path are blocked. For example, you can use techniques like transparent interconnection of many links or shortest path bridging software.
Converged Infrastructure and Apache Hadoop
Converged infrastructure works by combining multiple technology components into a single computing package. Some components of a converged infrastructure may include servers, data storage devices, networking hardware, and software for IT management.
Many customers are using converged infrastructure to build Apache Hadoop clusters. Apache Hadoop is an open source software framework written in Java for distributed storage and distributed processing of large data sets. Figure 3 shows a typical Hadoop cluster using Arista appliances.
In the leftmost core enclosure is a chassis with 12-port MXP line cards. Connected from the MXP line card are 24-pin MTP jumper wires that go into the MTP coupler panel. Each MXP line card has 12 ports, and each MTP coupler panel has 12 couplers mirrored on a pair of line cards.
On the back of the MTP coupler panel are 48 fiber MTP jumpers, two with 24 MTP jumpers used as backbone cables and connected to the back of the 24 port MTP-LC cassette module. Each 24-port cartridge module replicates a core switch to connect a row of compute enclosures.
The central cabinet or end-of-row or mid-row cabinet replicates four network core switches, two serving as primary data connections and two serving as management ports.
The cabinet on the right is the computer cabinet and has two rack top center cabinet switches. This configuration uses one central cabinet to store 10G or 25G of data and one central cabinet to manage 1G or 10G of data. The central cabinet switch is connected back to the central cabinet using an 8 fiber/4 port LC to LC cable assembly. Below the cabinet switches in the row in the computing cabinet are the servers and disk arrays.
All components of the data center
Converged infrastructure can contain all the components of a data center (servers, data storage devices, networking equipment, and software) in a set of cabinets or a single cabinet, as shown in Figure 4. As data center owners need more computing power, they can add infrastructure one rack at a time or multiple racks at a time.
When end users install these systems, in-cabinet connections can become a challenge due to the different types of media available. These media types include DAC copper cables, AOC active optical cables as well as traditional transceivers and optics with patch cords. Note that the DAC cable can be either passive or active.
In-cabinet connections using DAC cables
In-cabinet connections use DAC cables. DAC cables plug into network switches or uplink switches in servers and software appliances. Typically, DAC cables shorter than 5 meters are passive and consume no power. They do nothing to the signal and only act as a pass-through medium.
dac cable
The switches will set the signal conversion, conditioning, amplification and equalization or skewing before the signal enters the passive DAC cable. Proper utilization of passive DAC cables requires switches with signal processing chipsets to maintain acceptable skew.
Typically, DAC cables longer than 5 meters are active and draw power from both ends, but this can vary by manufacturer. AOC active cables cost, on average, three times as much as passive cables. SFP+ DACs are a popular choice for 10G Ethernet. It can reach up to 10 meters with low latency and lower cost.
One of the challenges of using a DAC is cable management. They come in standard lengths and breakouts, which can cause long service loops and cause cable congestion. Typically, DAC cables can support 1G to 1G, 10G to 10G, 40G to 40G, and 100G to 100G connections. They can also scale from 40G to 4x 10G and from 100G to 4x 25G.
In-cabinet connections using active optical cables
AOC active optical cables are made of fiber optic glass with optical components attached to both ends. They are more expensive than DACs, but can run longer distances and have higher speeds up to 100G.
aoc active optical cable
AOC active optical cables can support 10G to 10G, 40G to 40G and 100G to 100G connections. They can also scale from 40G to (4) 10G and from 100G to (4) 25G.
One limitation of using AOC active optical cables is that they only support one transmission speed and one type of supplier. When you do your next equipment upgrade, the AOC cable will most likely need to be replaced. Although cheaper than individual optics and jumpers, they do not scale to higher speeds.
In-cabinet connections using jumpers
Copper jumpers can be effectively used to operate at speeds from 1G to 10G when using transceivers installed in the device. Category 6 cable is the current industry leader for these connections.
The recently released miniature Category 6 cables reduce the diameter of standard Category 6 cables by 50%. Mini Category 6 cables also have more flexible copper cores for better routing inside the cabinet. It can be bundled in bundles and staggered at each end. One end can be interleaved into a ToR switch and the other end can be interleaved into any server or device port required.
Fiber patch cords and harnesses can be used effectively if the application uses a patch panel or central cabinet switch with the required optical ports. One of the advantages of using pre-terminated fiber is that the length can be precise to make the desired connection. Each connector can be pre-marked to the port destination for easy installation. This greatly reduces service loops within the cabinet and helps manage all other connections, such as power cords and monitoring equipment.
Another advantage is a longer potential lifespan. Unlike DAC cables with shorter lengths and lower power capabilities, fiber patch cords and harnesses will be forward compatible with speed.
Custom fiber optic harnesses can also be made to specific lengths and breakouts and pre-labeled for ease of installation and repeatability.
Hyperconverged Cabling
Hyperconvergence uses software architecture to integrate computing, storage, networking, virtualization and other technologies in a single hardware box. Hyperconvergence has now reduced the footprint to 1U or 2U of rack space as data centers begin to use converged infrastructure to bring computing systems into multiple cabinets (or just one cabinet).
This new technology relies on our development. The software communicates with all the required components in the computing cycle not only in one location but in many locations.
With us, Network Functions Virtualization has become the dominant enterprise data center model. The implications of these models are profound.
For example, an organization's primary data center might be located in its headquarters environment. The institution may be housed in a co-located facility at another local site. Using a large cloud provider like Amazon, it can also store its email and other business applications in the cloud. Each of these three locations could run the same wiring on their equipment, and the virtual network would allow them to appear and act as the same computing system for the user.
Hyperconverged In-Cabinet Connectivity
When deploying hyperconvergence, the rack space of the equipment used is 1U and 2U, and many devices can be installed in a single cabinet. Each of these devices typically requires two or four connections to the uplink switch. The uplink switch can be mounted on the top of the cabinet or in the center of the cabinet to reduce the length of connections within the cabinet.
Typically, hyperconvergence has more in-cabinet connections than three-tier topologies and converged infrastructure due to the large number of converged computers used per cabinet. Quickly understanding the necessary connections and optimizing the use of media types will reduce costs and provide optimal support for components in the enclosure.
cable kit
As data centers deploy hyperconvergence, proper planning can help prepare for in-cabinet connectivity. For example, it is highly recommended to determine the optimal length of DAC cables, breakouts, harnesses and power cords. Once the length of the power cord is determined, the two power strips can be color coded.
Additionally, selecting the necessary optics for each cabinet ahead of time will facilitate quick and efficient deployment. The optics can be programmed to work with equipment from several different suppliers to reduce the number of parts to order and manage. A single cable vendor box can contain all the connectivity and optical components required for a cabinet.
in conclusion
Data center topologies continue to migrate from three-tier to leaf-like. We are helping the evolution to converged infrastructure and hyperconvergence.
As the individual components used for computing come in smaller packages, such as 1U and 2U rackmount machines, cables are becoming more and more compact. The vast majority of connections are now done inside the cabinet and via DAC cables or AOC active optical cables.
Planning ahead and standardizing the location of cabinet equipment racks can help define the best cables for connections. Obtaining cables in the proper lengths, breaks, colors and labels will simplify installation, cable congestion, cooling and repeatability. This, in turn, will reduce connection-related downtime.
