RAY HAGEN SAVINGPOWER
REDUCING POWER IN THE DATA CENTRE IS CRUCIAL. PEBBLES IN THE OCEAN?
ProLabs Americas product manager Ray Hagen looks at reducing power consumption in data centres
case in point of a 10G SFP+ DAC cable. The combination of both ends requires 1.5W less power than two 10G SFP+ SR transceivers. 40G and 100G connections see even larger power consumption advantages with DAC cables. Applying these numbers to the real world, we need to answer the question, ‘In a world with 10-Megawatt data centres why should data centre managers care about 1.5 Watts?’ Like compounded interest on money, power savings in the data centre also compounds. As we include the power efficiency metric of the data centre, we also save on support power in the data centre. In this example, for each 1.5W of IT power savings, another 0.6 to 1.05 Watts of support power is saved. Offering a net savings of 2.1W to 2.55 Watts saved per connection. A data centre with a top- of-rack architecture and 1000 cabinets could realise up to 21kW power savings using DAC cables. The net effect on operating expenses comes in calculating the Kilowatt hour savings times the cost per Kilowatt hour. The cost of electricity may vary by up to 200% depending upon country and season. The regional data from the second half of 2017 proves out this assumption, data centres with higher power costs stand to gain the most from top-of-rack DAC connections. For example, while cost savings per year in the US could be over €10,700, In Ireland, they could top €20,400. However, using 100G QSFP28 for top-of-the-rack connections, these savings could hit €28,100 and €56,600 respectively.
A s data centres get increasingly larger, so does the amount of power they consume. Ray Hagen, Americas product manager at ProLabs looks at the numbers and ways in which consumption can be reduced significantly. If you asked a group of data centre managers around the world to rank their daily challenges, power would likely be one of the first items raised. Data centre power has the full attention of the C-suite, as both OPEX and CAPEX are impacted by power consumption and infrastructure. Global data centres measure their power capacity and consumption in Megawatts, not Watts. Thus incremental, ‘one-Watt-at a-time’ strategies may seem like throwing a pebble into an ocean, but given time and scale, they can reduce power consumption. Critical load generated by IT equipment like servers, routers and switches is only part of the power equation. Ancillary power for cooling, lighting, and other equipment must also be included in the data centre power consumption mix. Not all that long-ago data centres planned on a one-to-one ratio between IT critical load and support power. Meaning that for every Euro spent on critical load, one Euro was required for support power. This model did not scale well to the era of massive cloud data centres. Initiatives to improve data centre airflow, consolidate servers, advance the use of more efficient processors, cooling technology breakthroughs and raise the temperature in the data centre have dramatically improved power efficiency. Our same group of data centre managers may also tell you that these were the low hanging fruit for improving data centre power efficiency. The appetite
for increased investment in data centre efficiency is difficult with competing business needs. While the low hanging fruit may be gone, the pressure to reduce data centre power consumption has not faded away. Various metrics, such as Power Usage Effectiveness (PUE), are used to demonstrate the data centre support energy costs. Overall, today’s data centres tend to operate with an efficiency metric between 40% and 70% of the critical load. This means that for every 1 Watt of IT critical load used, 0.4W to 0.7W of support load is used. Thus, reducing the IT load by 1 Watt can lead to a reduction in total power load by 1.4 to 1.7 Watts. That is where looking at network cabling power offers opportunities for incremental efficiencies. Current data centre trends of top-of-rack switching are driving efficiencies one Watt at a time. Conventional top-of-rack architectures use direct attached cables (DACs) to connect servers in a rack to a switch in each rack. DACs are pre-terminated copper cable assemblies with a transceiver inserted into the SFP+ or QSFP port in a switch or server. In addition to being lower cost than a transceiver and structured cabling solution, DACs offer efficiencies by not performing optical to electrical conversion inside the module. The cost savings from not operating a laser offers a bare minimum of 70% power savings over a short reach transceiver,
Max Power Consumption -Watts (iNdustry example specifications)
SFP+
QSFP+ QSFP28
10G
40G
100G
DAC (one end)
0.11
<0.5W
<1W
Short Reach Transceiver (each)
0.880
1.5
3.0W
Figure 1: DAC vs Short Reach Transceiver
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| ISSUE 14 | Q3 2018
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