Blowing hot and cold on datacentre design
Jason Preston outlines his top tips for datacentre efficiency
New laws and a continuing need for cost containment are putting more pressure on datacentre managers to reduce power consumption and improve efficiency.
New state-of-the-art datacentres are achieving phenomenal efficiency ratings through the use of innovative technologies such as direct and indirect free cooling, with a strong emphasis on recycling and sustainability.
CIOs are being asked to move closer to efficiency nirvana – namely, a Power Usage Effectiveness (PUE) rating of 1.0.
Datacentre design is evolving at a phenomenal pace. Capgemini’s new state-of-the-art Merlin facility, for example, in my opinion takes datacentre thinking to a whole new level. Indeed, its innovative design and exploitation of leading edge technology has been rated as functioning at an amazing 1.08 PUE.
Few have the luxury of tearing down an existing datacentre and building a new one from scratch. So you have to improve the performance of your existing set-up. Efficiency is maximised, in part, from considering how air comes into the datacentre, how that air is cooled, how racks are arranged and where cables are laid.
The most obvious step is to configure cabinets in hot and cold aisles. Without doing this, it is extremely difficult to take advantage of any other technology innovations or implement design best practice that can make a difference to datacentre performance.
Avoid mixing cold air supplied from the air conditioning systems with hot return air from the IT equipment. For example, ventilated floor tiles need to be correctly placed within the 'cold' aisles and, preferably, be fitted with volume control dampers (VCDs).
Fit blanking panels to any cabinet-free space and fit brush-sealed grommets or blanks to any holes in a raised access floor, if it is being used as a supply-air plenum.
Install hot or cold aisle containment systems. Controlling every aspect of the supply air path from an air handling unit, through the servers and back, prevents recirculation and mixing of hot and cold air. This improves the operational efficiency of air conditioning systems. Both hot and cold aisle containment systems can be of benefit.
Increase cold aisle temperature
Increase the room (or cold aisle) temperature to between 24°C and 27°C. Too many datacentre managers still think their room should be kept below 19°C. The ASHRAE guideline for the server inlet temperature is 18°C-27°C, and it is now generally accepted by manufacturers that servers can run far hotter without affecting performance or resilience.
Install indirect or direct free cooling. The usefulness of these technologies is very site- and budget-specific, using specialised externally installed free-cooling plant coupled to traditional chilled water or DX gas CRAC systems.
This uses the outside ambient air temperature to transfer cooling to a water and glycol mixture piped to the indoor units via a closed circuit. Improvements in the efficiency of datacentre cooling of between 40-70 per cent are not uncommon when doing this.
Deploy high-efficiency UPS systems and consider using UPS in 'smart' or line interactive modes. New models of UPS are generally 96 per cent efficient in online mode with output power factors of 0.9, and in some case 1.0. Many will have line interactive or 'smart' modes where the inverter is turned off until the UPS senses an issue or disruption to the power supply.
Install voltage regulators or power-factor correction equipment, or both. The mains power supplied to many sites in the UK is either over the voltage required for the equipment installed, or the power factor is low. The use of voltage regulators will stabilise the voltage supplied to the datacentre at a defined level. Power-factor correction equipment will move the power factor as close to 1 as possible, for a reasonable cost.
These technologies can each deliver power cost savings of between 10-20 per cent.
Look at datacentre lighting. Wherever possible, opt for high-efficiency types with either compact fluorescent T5 or LED lamps and electronic control gear. Use proximity switching instead of standard switches, so once the area is vacated the lights will automatically turn off.
Replace legacy servers and storage with new high-efficiency equipment; for example, harness virtualisation to maximise performance of the equipment you already have.
Achieving effective datacentre design is a continuous and holistic process, with CIOs asked to balance cost cutting and green targets against business demands. Using real time insight into cabinet temperatures, humidity and energy consumption will provide both a strategic overview and effective day-to-day management.
Jason Preston is director of 2bm