best practice guide

8 Considerations for an Energy-efficient Data Centre

Traditional data centres are renowned for being among the most power-hungry ICT assets a business can own. In recent years, CIOs have come under increasing pressure to reduce power consumption in their data centres, given the ever-rising cost of energy. The mounting volumes of data which businesses need to manage have compounded the problem. Until recently, data growth inevitably meant the need for more data centres… and additional power consumption.

The good news is that next-generation data centre approaches and technologies provide a means to rein in spiralling energy costs. Follow these simple steps and an energy-efficient data centre – and impressive cost savings – will be within your reach.

latest thinking | 8 Considerations for an Energy-efficient Data Centre

latest thinking | 8 Considerations for an Energy-efficient Data Centre

Step 1: Consider alternative locations, and delivery and management models

The first critical step to achieving an energy-efficient data centre is to evaluate the various delivery and management options that have become available in recent years. Cloud computing opens new avenues of opportunity for data centre managers striving to improve energy efficiency. Today, there’s a strong move away from on-premise, enterprise-owned ICT infrastructure and data centres to cloud or hosted data centre models as businesses look to capitalise on the cost and efficiency benefits that this ‘as-a-service’ approach offers.

The next-generation data centre is becoming a place where multiple services that support the business are available as they’re required. You can procure a range of different permutations of service from your cloud provider(s), depending on your specific business requirements at a point in time. You can select a private, hosted, or public solution depending of the nature of the workload/data. The potential to shrink your data centre energy consumption dramatically with this approach has received significant attention of late. Modern, large-scale data centres are designed to operate at a higher level of energy efficiency. Further savings are realised from highly automated cloud and hosting data centres that allow you to turn off devices automatically when they’re not needed, and to pay for the devices (and the associated energy) only as they’re required.

Once you’ve considered what you want to run inside your own facilities and how you wish to procure and consume data centre services, the next step is to reassess the number of physical data centres that you need to own and operate. By optimising the delivery of applications over the network, you can reduce the number of data centres required. Fewer facilities usually mean less power consumption.

Then there’s the issue of data centre location. Traditionally, businesses built data centres in close proximity to their employees. A more modern approach is to position data centres in areas where the network performs optimally and to base employees in offices elsewhere. If you invest in automation and remote management tools, you no longer need people based at your data centre facilities.

Another approach is to increase the temperature at which your data centre operates. Traditional data centres run at cold temperatures as it was believed that this was ideal for the equipment. Recent thinking is that it’s possible to run data centres a few degrees warmer, making it more comfortable for staff, as well as reducing energy consumption. Increasing the temperature at which you run your data centre by just 5% can translate into cooling savings upwards of 10%. Another relatively new design approach is to position the computer room air conditioning (CRAC) and power units outside the walls of the data centre, which eliminates the heating influence of these devices. In addition, integrating the management of the infrastructure in your data centre facility enables the dynamic management of these elements and allows continual operation − at the optimal setting − based on current climate conditions as well as data centre load demands.

Step 2: Virtualise and consolidate

Virtualisation and consolidation are steps in the right direction towards an energy-efficient data centre. Many servers today still utilise between only 5 and 15% of their capacity, and service one application. With appropriate analysis and consolidation, many of these devices can be combined into a single physical server that consumes only a fraction of the power of the original devices – resulting in cost savings as well as creating a more environmentally sustainable data centre environment.

The basic concept of virtualisation is simple: encapsulate computing resources and run them on shared physical infrastructure in such a way that each appears to exist in its own separate physical environment. This process is accomplished by treating storage and computing resources as an aggregate pool that networks, systems, and applications can exploit, as needed.

Virtualisation and consolidation projects are complex, but the benefits are compelling: improved application availability and business continuity, independent of hardware and operating systems, among others.

Emerging server technologies that dramatically reduce power consumption deserve consideration, particularly for large-scale deployments.

‘ The good news is that next-generation data centre approaches and technologies provide a means to rein in spiralling energy costs.’

latest thinking | 8 Considerations for an Energy-efficient Data Centre

Step 3: Design a best-practice floor plan

The Uptime Institute produced a white paper based on a survey of 19 data centres and reported that, on average, only 40% of cold air went directly towards cooling the servers in the room, wasting yet more power in the data centre. So, whether you’re designing a new data centre or upgrading your existing environment, make use of existing best practices in data centre floor plan designs. Examples include:

Hot aisle/cold aisle layoutAdopting an alternating hot aisle/cold aisle layout is optimal and can correct many cooling problems in a typical data centre. By implementing a hot aisle/cold aisle layout, equipment is spared from having hot air recirculated, thereby eliminating the risk of an outage through device failure. Also, a common hot aisle gives you the ability to contain areas where heat density is high – such as racks with blade servers – and to deal with the heat in a specific manner. This allows for multiple heat-rejection methods to be in use within one data centre.

The distribution of power across racksAnother layout consideration is the distribution of power across racks. All attempts should be made to balance the watts per rack to within a 10-15% variance. This minimises hotspots and the need for sporadic hot-aisle containment. Often, data centre designers place servers performing related functions in the same racks, but the benefit of having these servers in close proximity is counteracted by the heat density this may cause. Isolation of dense server configurations where those units can operate at a higher temperature is the exception to this approach.

Minimise or eliminate underfloor cablingIt’s imperative for organisations with static pressure cooling to minimise or eliminate underfloor cabling. If you can’t avoid it, use conduit, cable trays, and other structured methods for running cabling. This minimises barriers between CRAC units and perforated tiles, resulting in more efficient airflow and optimised cooling system efficiency.

Step 4: Redesign the data centre network

Technology, architectures, and approaches for data centre networks have evolved significantly as organisations and the industry have put more focus on ensuring that the network is the platform for the modern data centre. Networking can contribute significantly to energy savings: the deployment of specialist data centre network hardware offers significant benefits over general-purpose network hardware. For example:

• front-to-back airflow to support hot/cold aisle layouts

• higher-efficiency power supplies that dramatically reduce power consumption per port

• convergence functionality to enable the consolidation of multiple devices into a single appliance, which in turn reduces the number of cable runs and improves airflow through the entire data centre

Step 5: Use appropriate technology

In your quest for an energy-efficient data centre, your evaluation of products can no longer be just a price-versus-performance comparison. It’s important to incorporate the total cost of the data centre environment into the calculation, which also includes costs for energy consumption.

Firstly, look for vendors that have power and cooling at the forefront of their research and development strategies. Secondly, select equipment based on lifecycle costs that take into account the energy usage of servers.

An example of an energy-efficient technology is massive array of idle disks. This is a storage technology that employs a large group of disk drives. Only those drives in active use are spinning at any given time. This technology can have thousands of individual drives, and offers mass storage at a cost per terabyte roughly equivalent to that of tape.

latest thinking | 8 Considerations for an Energy-efficient Data Centre

Step 6: Take a new perspective on information life cycle management (ILM)

ILM is the optimum allocation of storage resources that support a business. From a voice conversation to legal and medical records, every item of information in an organisation has a useful lifespan. By implementing an ILM strategy, you can create greater efficiencies in data storage, which in turn lead to greater efficiencies in power consumption.

ILM is the application of rigour to the often chaotic and unstructured data stores that an organisation maintains. The storage, utilisation, maintenance, and destruction of this data can be quite expensive over its lifetime – a lifetime that’s often much longer than the data’s useful life. The art of ILM lies in understanding your organisation’s information needs and developing the infrastructure and processes required to maintain the usefulness of that information, while at the same time minimising the cost of such maintenance.

The value of ILM is the ability to tie the cost of storage to the value of the information stored. Tiered storage is therefore at the heart of an ILM implementation. The most important data, or the most performance-critical data, should be placed on the highest-performance and most expensive storage. Don’t use expensive, energy-consuming storage to store information for compliance purposes, when a tape will do. Take advantage of low-speed and lower energy-consuming devices whenever they can meet the service requirements. Increasingly, solid-state drives are becoming part of the enterprise architecture, providing performance improvements; however, these decisions should be made while bearing the associated energy trade-offs in mind.

Additionally, knowing the character (age, file type, usage frequency, and business value) of the data in your environment will help you make informed decisions about ILM strategies. Assessments that Dimension Data has conducted with more than 100 organisations worldwide show an average of more than 40% file duplication in their environments.

This information provides organisations with the insights they need to decide whether to move data to less expensive and lower-energy consuming storage, and how to better utilise their existing environments and save storage space by taking advantage of compression and de-duplication. Finally, moving information completely out of the data centre to cloud or archival solutions can drive dramatic reductions in on-site consumption.

Step 7: Investigate liquid cooling

To meet the challenges of blade servers and high-density computing, more organisations are realising the need for effective cooling and heat management solutions. Many are welcoming liquid cooling systems into their infrastructures to achieve better cooling efficiency; however, others still find it difficult to fathom pipes of running water snaking through the plenums of their data centres.

Liquid cooling systems use air or liquid heat exchangers to provide effective cooling and to isolate equipment from the existing heating, ventilation, and air conditioning system. There are several approaches to data centre liquid cooling:

• Sidecar heat exchangers − closed enclosures that deliver cooling from the side, which prevents it from dissipating into the server room.

• Chip-level cooling and bottom-mounted heat exchangers − these enclosures use a bottom-mounted heat exchanger, which some claim is safer than sidecar enclosures as components won’t be affected in the event of a water leak.

• Modular liquid cooling units − used within a fully sealed cabinet and mounted at the rack base, in a rack sidecar.

• Door units − full-door units that replace a standard server rack door and contain sealed tubes filled with chilled water.

• Integrated rack-based liquid cooling − incorporates a rack-based architecture that integrates uninterruptible power supply, power distribution and cooling, and features a cooling distribution unit that pumps water through aluminium or plastic tubing to cool servers.

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• Device-mounted liquid cooling − works at the device level, with coolants routed through sealed plates on the top of a CPU.

While liquid cooling provides the best thermal transfer and most efficient removal of heat from the data centre, frequently a better alternative is to leverage free air for all or some of the year, depending on the climate. This approach makes climate a key consideration in data centre location.

Step 8: Use power-saving technologies

There are a number of power-saving technologies available. For example, direct current (DC)-compatible equipment can have a significant impact on power consumption; however, it’s costly to configure, is not widely available, and is also more expensive than equivalent alternating current options.

At present, data centres perform many conversions between alternating current and direct current. This wastes energy, which is emitted as heat and increases the need for cooling. It’s far more efficient to power servers directly from a central DC supply. The Lawrence Berkeley National Laboratory in the US estimates that an organisation may save 10-20% of its energy use by moving to direct current technology.

Alternatively, consider deploying higher-voltage air conditioning within the data centre when this is suitable for the technologies deployed. In some cases, elimination of step-down transformer and distribution losses can reduce energy loss by up to 10%.

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