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FEATURE DATA CENTRE OPTICS


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Super-sizing the data centre


Warehouse-scale data centres are stretching the limits of current networking technologies. Dr Ioannis Tomkos describes how advanced optics can remove performance bottlenecks to enable the data centres of the future


preferred method for getting around the company’s warehouse-sized facilities. Google builds some of the largest data centres in the world, although it considers the precise details to be commercially sensitive. One thing is clear, however; data centres are getting bigger and bigger, and this has major implications for the way they are designed. Data centres are expanding because they have to


W Spine


handle an ever-increasing workload. From cloud computing applications, streaming video and online gaming to scientific simulations, financial


hen Google published an insider’s view of its data centre operations, one image showed a branded bicycle that is their employees’


technologies, and the Internet of Tings (IoT), a myriad of new applications have significantly increased the traffic that needs to be handled by data centres. In this new cloud computing era, warehouse-scale computers are needed to process user data that no longer reside at a local computer, but are stored in the ‘cloud’. Te hardware to support such a cloud platform


consists of thousands of individual computing nodes with their corresponding networking and storage subsystems, power distribution and conditioning equipment, and extensive cooling systems, housed in a building structure that is called a data centre. In today’s operational data centres, the total number of powerful servers can scale to several hundreds of thousands. Terefore, to further emphasize the massive size of this new generation of data centres, people characterise them as ‘warehouse-scale’ or ‘mega’ data centres. Each and every one of these edge and core data


centres processes enormous amounts of traffic and collectively they handle the majority of the entire cloud data. According to Cisco’s Global Cloud Index, the annual global IP traffic passing over data centre networks is expected to exceed 10.4 zettabytes by the end of 2019, with cloud data centre


Figure 1: A spine-leaf architecture connecting all servers together


traffic accounting for more than four fiſths (83 per cent). Furthermore, it is forecast that, by 2018, nearly four out of five workloads will be processed by these cloud data centres. In fact, the traffic we see exchanged over


telecoms networks is only the tip of the iceberg; there is also a massive increase in internal or intra-data centre network (intra-DCN) traffic. It is worth emphasising that, based on the Cisco’s analysis of the distribution of the entire data centre traffic, about 75 per cent of the traffic is contained within the data centre, while only about 25 per cent actually leaves the data centre – whether travelling to the end user, or as workloads are moved from one data centre to another.


Scaling up operations One option to scale the capabilities of these data centres to support current and future cloud computing applications is to incorporate more powerful servers based on higher performance processors. Another option to scale up the performance of such data centres is to increase the number of powerful servers that they encompass. In either case, a powerful, ultra-high-capacity intra-DCN is required to connect the servers and switches. To put things into perspective, consider that a data centre with 100,000 servers would require an internal network with more than one petabyte of aggregate bandwidth to support bi-directional communication among all servers! Te main limiting factor of the size of such a data


Leaf (ToR)


centre, however, may not be the internal network capacity, but the electrical power that is required to sustain its operation. When the number of elements is scaled up into the hundreds of thousands, the consumption of electronic circuits and systems becomes a force to be reckoned with. Tis is why data centres operators oſten try to locate new buildings near cheap or renewable sources of electricity, or in regions with cold air for cooling. A more radical way to scale up the capabilities of


Server/ Storage


data centre operations would be to deploy many, perhaps smaller, data centres, so that they can be located closer to the end users, and each data centre would be less demanding in terms of its individual power and capacity requirements. In this case, and


22 FIBRE SYSTEMS Issue 11 • Spring 2016


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