Sustainable Data Centres Approaches and Challenges. * Corresponding author: t.s.luong@student.reading.ac.uk

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1 Proceedings of Conference: TSBE EngD Conference, TSBE Centre, University of Reading, Whiteknights Campus, RG6 6AF, 6 th July Sustainable Data Centres Approaches and Challenges S. Luong 1*, K. Liu 1, S. Chong 2 1 Technologies for Sustainable Built Environments, University of Reading, UK 2 Capgemini UK, Sale, UK * Corresponding author: t.s.luong@student.reading.ac.uk ABSTRACT Data centres are increasingly becoming an essential component for many organisations. With the emergence of highly sophisticated and integrated IT services the market is demanding for more computing and storage power. This means that data centres are expanding at a remarkable rate in response to demand. While this may bring more business for an organisation they have started to realise their environmental objectives and the statistics of a data centres energy consumption. Having reviewed the current issues of sustainable data centres, this is an introductory paper that proposes a research objective on the sustainable applications of data centres. The proposed solution highlights the use of agent technology for cooling systems in a data centre environment and whether a preemptive cooling system is more energy efficient than a reactive cooling system. Keywords: Data Centres, Sustainability, Green Technology 1. INTRODUCTION This paper introduces what a data centre is, and the application of sustainability to an intensive energy-consuming company asset. The aim is to provide an abstract overview of a new research project that is in progress at the TSBE Centre, University of Reading in collaboration with Capgemini UK. The motivation behind this project is to highlight and tackle the issue of energy consumption and carbon emission footprint in data centres. If no action is taken now data centres could potentially be aligned next to transportation and buildings as one of the most environmentally harmful human systems. 1

2 Organisations around the world are under increasing pressure to conduct business in a more environmentally friendly way. Many of them rely on data centres to run their business activities and IT services. To emphasise the severity, the UK has committed themselves to reduce carbon emissions by large low energy-intensive organisations by approximately 1.2 million tonnes per year by 2020, and to reach an 80% reduction by 2050 (DECC, 2010). A mandatory carbon trading scheme that started in in April 2010, governed by CRC Energy Efficiency Scheme (2009), will have an impact on larger businesses. This impending consequence raises a research question: is it possible to reduce energy consumption and carbon emissions from data centres and maintain support for growth and continuity for a sustainable business. The research project revolves around the philosophy of sustainability and how it is applied to data centres. The paper is presented as follows. In section 2, we describe what a data centre is, its history and infrastructure. Section 3 discusses the topic of green and sustainability in the context of data centres. An assessment of the current state-ofthe-art energy-aware technologies in data centres is presented in section 4. Finally, we conclude and lay the basis of our future work plan in section DATA CENTRES A data centre is defined as a facility used for housing a large amount of computer and communications equipment maintained by an organisation for the purpose of handling the data necessary for its operations (MSDN, 2010). While this definition abstract it is actually referred to as typically, the facility and floor space is occupied mainly by IT equipment. In the IT industry, a data centre houses the state-of-the-art service provider technologies hosted by computer servers, storage devices and networking equipment. They are some of the most expensive hardware that any organisation would purchase to support the business operations and activities. They are identified as major asset to the organisation due to its role in the organisation and the invaluable data it stores. 2.1 Data Centre History The history of data centres started when the microcomputer industry was introduced in the 1980s. The IT equipment were large, room sized machines that needed cables to connect all the components together and a special environment to operate in. Maintaining and operating these machines was a highly complex task because each component performed a particular function and cable management was vital to ensure that the administrators were able to identify each component and how they communicate. This led to the practice of isolating them into dedicated rooms. Initially, the military were using these machines. They were very expensive and the need for heavy security was deployed to control access to the machine. Eventually, other organisations and businesses invested in these computers for their own ventures. Due to the equipment consuming huge amounts of power they would generate lots of heat. Cooling systems were essential to allow the machines to function without overheating another reason to keep the 2

3 expensive equipment in a dedicated, climate controlled environment. Eventually, computers were being installed everywhere as a way of helping organisations to perform their operations and establishing internet presence. The birth of data centres was marked in the 1990s when companies tried to reduce the complexity of the IT equipment by organising them in a controlled environment. This led to the introduction of the client-server architecture and so the computer servers found themselves a home in a closet or dedicated rooms. 2.2 Controlled Environment The IT equipment in a data centre benefits from a luxurious environment with many other expensive hardware to ensure that it lives in a controlled and optimal environment. The four primary components of a data centre consist of the following: 1. Electrical power includes the primary and standby power generators that are located on site, the distribution units for directing power to the required locations and conversion adaptors from converting AC power from the grid to DC power. 2. Cooling includes chillers for dissipating heat from water via heat exchangers, heaters and air conditioning to ensure the environment is at the correct temperature and ventilation for the intake of external air and exhaust for hot air. 3. Floor space and cable management includes the management of maximising floor space, using raised floor to improve cooling capabilities and under floor or overhead cable conveyance. 4. Practices and management includes being compliant with local legislations, internal policies and regulations, International Standards Organisation (ISO) guidelines and environmental health and safety. The above are the essential components for a data centre environment (Schulz, 2009). There are many other components that make up a data centre but not all are essential as they vary in size, shape, what it was designed for and technology preference. 2.3 Data Centre Classification As of current, the Uptime Institute of America (2010) has defined (and updated) four tiers of data centres, which was reviewed by the Telecommunications Industry Association (2006). Organisation s design and construct their data centres to these requirements and aim to be certified by the Uptime Institute of America to reduce risk and cost, and achieve long-term business value. Tier 1 represents the lowest availability and level of protection, and tier 4 being the highest cost to implement and most expensive environment. The four tiers are: 3

4 Table 2: Four tier data centre classification Tier 1 Tier 2 Tier 3 Tier % Availability - Tier 1 requirements - Tier 2 requirements - Tier 3 requirements - Single distribution path % Availability % Availability % Availability - No redundancy (N) - Single distribution path - N+1 - Multiple distribution paths - Concurrently maintainable - Multiple independent distribution paths - Fault tolerance for all components The requirements outline the level of infrastructure to sustain normal operations. It takes into consideration the annual down time, the number of paths for power and cooling distribution, whether it includes redundant components, maintenance and fault tolerance. For example, a tier 2 data centre includes the requirements of tier 1, allows an annual down time of 22 hours, single path for power and cooling, and the main set of components has been mirrored (N+1) so there are two identical set of components. A tier 4 data centre includes the requirements of the previous three tiers but this type of data centre can sustain a worst case disruption scenario with multiple paths for power and cooling but from different independent sources, multiple redundant components and an annual downtime of 24 minutes. 2.4 Cooling & HVAC (Heating, Ventilation & Air Conditioning) Cooling and HVAC must be incorporated into the design stage of a data centre as there are many ways of providing cool air to the IT equipment. Power and network cables can be located on the floor and air conditioning provided through the ducts in the ceiling. The physical layout of the data centre varies as there is no single configuration. However, for more efficient cooling a raised floor solution offers practical benefits in comparison to a non-raised floor as discussed by Schulz (2009), Snevely (2002), Uptime Institute (2010) and TIA-942 (2006) Data Centre Standards. Additionally, the server cabinets should be arranged to form a hot and cold aisle. The cabinets are placed face to face on a raised floor. The front of the cabinets is facing each other in an alternating pattern. The power and network cable conveyance are placed underneath the raised floor. The front of the cabinet draws cold air from the floor through perforated tiles and expels hot air out the back. The hot aisle has no perforated tiles to prevent the hot and cold air from mixing. A typical room layout portrayed in figure 2.1 shows how conditioned air is forced into the supply plenum and kept pressurised so that the air can escape through the perforated tiles. The servers in the cabinets draw the cold air from the supply 4

5 plenum. Hot air is expelled out of the cabinets and rises up to the return plenum. The CRAC units restart the whole cooling process by drawing hot air from the return plenum. Figure 2.1 Cold air / hot air plenum In figure 2.2 both ends of the room have computer room air conditioning (CRAC) units. The cabinets are aligned in rows so that the hot aisle and cold aisle are separated. In order to maximise the cooling efficiency this type of configuration uses raised floors and ceiling tiles to create plenums: cold air (supply) plenum and hot air (return) plenum. Figure 2.2 Hot Aisle Cold Aisle Configuration The cooling configurations described here are reaching its limitations as component footprint per square feet of floor space is increasing; therefore using more power and generating more heat. The cooling units are reaching maximum capacity and this could be a serious problem for the future of data centres. 3. DATA CENTRE SUSTAINABILITY The two most widely used definitions of sustainability are: 5

6 1. conserving an ecological balance by avoiding depletion of natural resources (Oxford, 2010) 2. meeting the needs of the present without compromising the ability of future generations to meet their own needs (UN Documents, 1987). They both imply the principle of not causing irreversible environmental damage. The term sustainability is widely applied to human sustainability on planet Earth. There are many theorised problems that humans are going to encounter in the foreseeable future. On the current development model the Department of Economic and Social Affairs (2008) estimated that the population will increase to over 9 billion by There will not be enough resources for distribution to everyone as the Earth has a fixed amount of natural resources. Electricity is generated by burning fossil fuels: its major by-product is carbon dioxide and it is a limited resource. However, carbon dioxide is one of the greenhouse gases that are produced by human activities. There are strong evidence linking greenhouse gases to anthropogenic causes and if no action is taken now it would cause irreversible damage to the environment. Statistics show that data centres are heavy consumers of electricity. In the United States, data centres consumed $4.5 billion of electricity alone with a predicted growth rate at 12% per year (Scheihing, 2009). In Western Europe, the European Commission (2008) estimated that data centres consumed 56 TWh per year in Based on the Department of Energy and Climate Change s (DECC, 2008) price assumption this estimates to 3.14 billion. If data centres continue to grow at its current pace it will put immense strain on power stations to produce more electricity, which means more fossil fuel has to be burnt and therefore seriously increasing the carbon footprint of the data centre. 3.1 Difference between Green & Sustainability Over the years, the word green and sustainable has been used interchangeably, which has caused much confusion as to be green is not the equivalent of to be sustainable. The word sustainable has been diluted for commercialisation, which does not help those trying to understand the philosophy of sustainability. To be green is to change your life style to be more environmentally friendly, use energy efficient products, reusing and recycling waste and water, etc. But to be sustainable is actually going beyond just being green. Sustainability is a continuous process lasting indefinitely or to simply put it to be zero energy. Being sustainable is to use sustainably harvested or renewable sourced products without causing irreversible damage to the ecosystem. Realistically, applying the definition of sustainability to data centres could be an impossible task given the circumstances of our economy and how the world relies on energy to exist. In this context, we could only follow the guidelines of making data centres use energy responsibly and restore, as much as possible, whatever has been consumed. 6

7 3.2 The Sustainable Data Centre A green data centre is designed for maximum energy efficiency and minimum environmental impact. Although this is achievable through advancing technology and strategy this will not solve the long term issue. We will attempt to differentiate a green data centre from a sustainable data centre. A sustainable data centre should provide normal business operations with as close to having a zero environmental impact as possible under current technology constraints whilst maintaining economic growth. Our definition here suggest that rather than just focusing on greening the data centre we should ensure the data centre fits to the organisations mission statement of meeting their environmental targets. However, it should extend further to meeting local or even enterprise targets of minimising their long term impact to the environment by working within the technology barriers and offer flexibility for the business to respond to future demands. It could be the case that a data centre uses a wind farm, PV panels and fuel cell technology to supply power as the technology is already available. It also means to play its role as not a single entity but part as a global wide initiative of helping the organisation, government and the country to meet its environmental objectives. It is inevitable for a data centre to expand and continue to grow. But, if advancement in technology presents an opportunity for the greater good and operating sustainably then that organisation should take responsibility and use new technology where possible to help sustain the long-term strategy of preserving the environment for future generations. 3.3 Standards and Guidelines There are a number of standards and guidelines to which a well-built data centre should conform. Besides the Data Center Site Infrastructure Tier Standard by the Uptime Institute of America there are four other standards and guidelines a data centre design should adhere to in order to maximise energy efficiency, minimise environmental impact and improve environmental health and safety. The ISO standard set the requirements for an environmental management system (EMS) and guidelines for keeping a log of the environmental performance by managing the environmental impact, continuously improve performance, and action objectives and targets in a systematic approach. ASHRAE Environmental Guidelines for Datacom Equipment set recommendations for data centre temperature operating range and conditions. The guidelines offer greater flexibility for data centre operators to set their temperature and humidity controls slightly higher than they normally would in order to reduce energy consumption. The Code of Conduct on Data Centres Energy Efficiency is a voluntary initiative designed by the European Commission that provides a set of aims and targets, which helps minimise energy consumption and best practice for managing data centre activities. OHSAS outlines the assessment specification for Occupational Health and Safety Management Systems to ensure organisations understand their obligations to improve the management of health and safety. 7

8 Organisations are only starting to realise the impact their business operations have on the environment. They have begun adopting standards and guidelines in response to recent legislations and policies that have been established. However, it is not certain that these standards and guidelines could be an inconvenient checklist that an organisation feels they are obliged to comply with to avoid penalties. It is certain that when technology advances further and more energy are required then these standards and guidelines will need to be revised once again to meet demands of the future. 4. CURRENT APPROACH TO SUSTAINABLE DATA CENTRES As data centres are a very complex system involving many components there are various areas that could benefit from research into reducing energy consumption. Some of the methodologies and practices that industry is currently using are consolidation, virtualisation technology, thermal management and modular design and implementation. Recent research by Srikantaiah et al. (2008) looks at energy optimisation through consolidation in a cloud computing environment. The problem discussed here is the idle power wasted when servers run at low utilisation. The solution designed is a consolidation algorithm that utilises the low energy servers but within performance constraints therefore reducing energy costs without affecting performance. Other research into consolidation for energy reduction has been carried out by Nathuji and Schwan (2007), Torres et al. (2008) and Song et al. (2009). Whilst consolidation may help reduce energy cost, total cost of ownership and underutilised servers it does not solve the long term fact that more servers has to be installed to support future demand. Also, delivering a consolidated strategy is complex as there is a risk of devising the wrong methodology which could result in over-utilising each physical server. Generally, energy saving techniques at hardware level is more popular in industry as hardware is simply plug and play and receives immediate results. IBM, one of the leading server vendors, revived a 40 year old technology to use water cooling at chip level and supply the wasted heat to nearby offices therefore reducing energy consumption and carbon dioxide emissions (IBM, 2009). Another research paper written by IBM researchers discusses the use of dynamic voltage scaling (DVS) that varies the processor frequency and voltage for energy saving purpose without affecting system responsiveness and performance (Elnozahy et al., 2003). Lee and Zomaya (2009) evaluated the use of DVS based on energy-aware task scheduling algorithm which is fairly similar to the former research. This is a very valuable piece of research as more processors are being compacted onto a rack. But this could also have a negative approach: if all processors on a rack are at 100% utilisation, as it will generate heat very quickly and therefore much more cooling is needed. Cooling and HVAC has been continuously refined and upgraded in order to provide more cooling capacity, energy efficiency and cost reduction. Recent research work evaluated the use of computational fluid dynamics (CFD) to determine and 8

9 optimise the thermal and airflow pattern of the data centre (Romadhon et al., 2009). By analysing where most of the heat is generated and the effectiveness of the cooling system they are able to optimise and configure the rack arrangement to distribute heat evenly and improve the cooling and air flow. Other in-depth discussions include an analysis of thermal plumes in the upper regions of a data centre (Cho and Awbi, 2009). There is a lot of research in this area by both academic and industry as most of the energy is consumed by the cooling and HVAC systems rather than the IT equipment. The main objective is to ensure IT equipment consumption is as close to or equivalent to the power input to a data centre. 5. CONCLUSION & FUTURE WORK Global warming and climate change are the two major topics that are currently being discussed everywhere. With the problems being associated to human activities the UK government will eventually start introducing schemes and legislations in favour of reducing environmental impact. Organisations are starting to take action for their responsibilities by conducting business with sustainability in mind. They are setting themselves carbon emission and energy reduction targets which in the end will help them save money and be environmentally friendly. We have introduce what a data centre is, followed by the definition of sustainability and how it is applied to the concept of sustainable data centres. The state-of-the-art technology present that a lot of research is in progress into many different components of a data centre. In future work, we will focus on one particular component of the data centre cooling and HVAC systems. The research will consist of collecting raw data from industry, extensive literature review of sustainability, data centres, intelligent agents and air conditioning systems and the design of intelligent zoned air conditioning system for data centres. REFERENCES ASHRAE, 2008, Environmental Guidelines for Datacom Equipment Expanding the Recommended Environmental Envelope, The American Society of Heating, Refrigerating and Air-Conditioning Engineers, USA. Cho, Y. J., Awbi, H. B., 2009, Analysis of thermal plumes in a data centre hall, 11 th International Conference on Air Distribution in Rooms, 2009, Busan, Korea. CRC, 2009, Carbon Reduction Commitment Energy Efficiency Scheme, Carbon Reduction Commitment, [online] Available at: [Accessed 05 June 2010]. DECC 2008, Department of Energy & Climate Change, Digest of United Kingdom Energy Statistics, 2008 Edition. DECC, 2010, CRC Energy Efficiency Scheme, Department of Energy & Climate Change, [online] Available at: [Accessed 05 June 2010]. DESA, 2008, Population Newsletter, Department of Economic and Social Affairs Population Division, New York, USA, Number 87. 9

10 Elnozahy, M., et al., 2003, Energy Conservation Policies for Web Servers, 4 th Conference on USENIX Symposium on Internet Technologies and Systems Volume 4, Seattle, WA. European Commission, 2008, Code of Conduct on Data Centres Energy Efficiency Version 1.0. IBM, 2009, IBM and ETH Zurich Unveil plan to build new kind of water-cooled supercomputer, IBM Press Room, [Online] Available at: [accessed 05 June 2010]. ISO, 2008, ISO Essentials, International Organization for Standardization, International Standards for Business, Government and Society, [online] Available at: [Accessed 05 June 2010]. Lee, Y. C., Zomaya, A. Y., 2009, Minimizing Energy Consumption for Precedence-constrained Applications Using Dynamic Voltage Scaling, 9 th IEEE/ACM International Symposium on Cluster Computer and the Grid, 2009, ISBN MSDN, 2010, Glossary of MMC Terminology, Microsoft Developer Network, [online] Available at: [Accessed 05 June 2010]. OHSAS, 2007, OHSAS Health and Safety, Occupational Health & Safety Standards, [online] Available at: [Accessed 05 June 2010]. Oxford, 2010, Oxford Dictionaries, [online] Available at: [Accessed 05 June 2010]. Nathuji, R. Schwan, K., 2007, VirtualPower: Coordinated Power Management in Virtualized Enterprise Systems, SOSP 07, Washington, USA. Uptime Institute, 2010, Uptime Institute LLC, Data Center Site Infrastructure Tier Standard: Topology. Romadhon, R., et al., 2009, Optimization of Cooling Systems in Data Centre by Computational Fluid Dynamics Model and Simulation, Innovative Technologies in Intelligent Systems and Industrial Applications, 2009, ISBN Scheihing, P., 2009, U.S. Department of Energy, Energy Efficiency and Renewable Energy, DOE Data Center Energy Efficiency Program. Schulz, G., 2009, The Green and Virtual Data Center, CRC Press, Minnesota, USA, ISBN Song, Y., et al., 2009, Utility Analysis for Internet-Oriented Server Consolidation in VM-Based Data Centers, Cluster Computing and Workshops, 2009, IEEE International Conference, ISBN Srikantaiah, S., et al., 2008, Energy Aware Consolidation for Cloud Computing, Microsoft Research, USENIX, USA. 10

11 TIA-942, 2006, ADC Telecommunications Inc, Data Center Standards Overview. Torres, J. et al., 2008, Reducing Wasted Resources to Help Achieve Green Data Centers, IEEE International Symposium on Parallel and Distributed Processing, 2008., ISBN UN Documents, 1987, Our Common Future, Chapter 2, Towards Sustainable Development, [online] Available at: [Accessed 05 June 2010]. 11