ExaNest is one of three European projects that support a ground-breaking computing architecture for exascale-class systems built upon power-efficient 64-bit ARM processors. This group of projects share an 'everything-close' and 'share-anything' paradigm, which trims down the power consumption - by shortening the distance of signals for most data transfers - as well as the cost and footprint area of the installation - by reducing the number of devices needed to meet performance targets. In ExaNeSt, we will design and implement: (i) a physical rack prototype and its liquid-cooling subsystem providing ultra-dense compute packaging, (ii) a storage architecture with distributed (in-node) non-volatile memory (NVM) devices, (iii) a unified, low-latency interconnect, designed to efficiently uphold desired Quality-of-Service guarantees for a mix of storage with inter-processor flows, and (iv) efficient rack-level memory sharing, where each page is cacheable at only a single node . Our target is to test alternative storage and interconnect options on actual hardware, using real-world HPC applications. The ExaNeSt consortium brings together technology, skills, and knowledge across the entire value chain, from computing IP, packaging, and system deployment, all the way up to operating systems, storage, HPC, big data frameworks, and cutting-edge applications

The growth in demand for Information Technology (IT) systems and the requirements to better control carbon emissions is a large challenge for data centre design. Aircooled data centres are becoming more efficient by layout and the adoption of compressor free cooling, but for higher densities, further efficiencies can be achieved with liquid (water) cooled systems, where liquid is either brought to the cabinet or is fed directly into the IT systems. This paper makes a comparison of the full energy consumption between hybrid air-cooled and direct liquid-cooled systems based on real operational systems using comparable IT components. The results based on real data demonstrate a significant level of energy reduction for a high density data centre solution that uses enclosed, immersed, direct liquid-cooled servers.

Liquid immersion of datacom electronics can be configured as a cooling mechanism when components are in direct contact with a high dielectric strength liquid. This paper analyses the heat transfer capabilities of datacom electronics when they are enclosed in a cassette with a dielectric liquid and sandwiched against a cold plate positioned in parallel with the printed circuit board. A proxy server motherboard with controllable heat cells and temperature sensors is used to conduct a series of heat transfer experiments. The results of which demonstrate that the thermal conductance processes via the naturally convecting dielectric liquid improves as the power demand of the electronics increases.

No abstract