Impact of Shutdown Techniques for Energy-Efficient Cloud Data Centers

International audienceElectricity consumption is a worrying concern in current large-scale systems like datacenters and supercomputers. These infrastructures are often dimensioned according to the workload peak. However, their consumption is not power-proportional: when the workload is low, the consumption is still high. Shutdown techniques have been developed to adapt the number of switched-on servers to the actual workload. However, datacenter operators are reluctant to adopt such approaches because of their potential impact on reactivity and hardware failures, and their energy gain which is often largely misjudged. In this article, we evaluate the potential gain of shutdown techniques by taking into account shutdown and boot up costs in time and energy. This evaluation is made on recent server architectures and future hypothetical energy-aware architectures. We also determine if the knowledge of future is required for saving energy with such techniques. We present simulation results exploiting real traces collected on different infrastructures under various machine configurations with several shutdown policies, with and without workload prediction

Energy aware approach for HPC systems

International audienceHigh‐performance computing (HPC) systems require energy during their full life cycle from design and production to transportation to usage and recycling/dismanteling. Because of increase of ecological and cost awareness, energy performance is now a primary focus. This chapter focuses on the usage aspect of HPC and how adapted and optimized software solutions could improve energy efficiency. It provides a detailed explanation of server power consumption, and discusses the application of HPC, phase detection, and phase identification. The chapter also suggests that having the load and memory access profiles is insufficient for an effective evaluation of the power consumed by an application. The available leverages in HPC systems are also shown in detail. The chapter proposes some solutions for modeling the power consumption of servers, which allows designing power prediction models for better decision making.These approaches allow the deployment and usage of a set of available green leverages, permitting energy reduction

IT Optimization for Datacenters Under Renewable Power Constraint

International audienceNowadays, datacenters are one of the most energy consuming facilities due to the increase of cloud, web-services and high performance computing demands all over the world. To be clean and to be with no connection to the grid, datacenters projects try to feed electricity with renewable energy sources and storage elements. Nevertheless, due to the intermittent nature of these power sources, most of the works still rely on grid as a backup. This paper presents a model that considers the datacenter workload and the several moments where renewable energy could be engaged by the power side without grid. We propose to optimize the IT scheduling to execute tasks within a given power envelope of only renewable energy as a constraint

On the Energy Efficiency of Sleeping and Rate Adaptation for Network Devices

Best Paper AwardInternational audienceThe ever-growing appetite of Internet applications for network resources has led to an unprecedented electricity bill for these telecommunication infrastructures. Several techniques have been developed to improve the energy consumption of network devices. As their utilization highly varies over time, the two main techniques for saving energy, namely sleeping and rate adaptation, exploits the lower work-load periods to either put to sleep some hardware elements or adapt the network rate to the actual traffic level. In this paper, we compare two emblematic approaches of these energy-efficient techniques: Low Power Idle and Adaptive Link Rate. Our simulation-based study quantifies the reachable energy savings of these two approaches depending on the traffic characteristics. We show that, with little impact on the Quality of Service and consequent energy savings, Low Power Idle has a clear advantage. On the contrary, ALR is almost always consuming more than LPI and can reach unacceptable QoS levels. We also show that they can be combined to achieve better energy-efficiency, but at the cost of important QoS degradation

CD44 is highly expressed in stem/progenitor cells originating the intervertebral discs in the human notochord

Objective: The notochord acts as a patterning structure, playing a key role in the formation of the vertebral column, both indirectly by inducing sclerotome cell differentiation and directly by forming the nucleus pulposus of intervertebral discs. The abnormal development of the notochord results in an easy equation with a variety of birth defects. Therefore, we focused our attention on the analysis of the early stages of human notochord development by highlighting the role of progenitor stem cells involved in the origin of intervertebral discs (IVDs). Materials and methods: Eight human fetuses, ranging from 8 up to 21 weeks of gestational age, were obtained from spontaneous abortion or voluntary interruption of gestation. Samples were 10% formalin-fixed, routinely processed, and paraffin-embedded. Five micron-tick paraffin sections were obtained from each sample. Sections were stained with hematoxylin-eosin and PAS stain for a morphological examination. Tissue samples were immunostained with a commercial anti-human CD44 rabbit monoclonal antibody at 1:100 dilution. Results: Immunoreactivity for CD44 was detected in six out of eight notochords examined in this study. Reactivity for CD44 was restricted to progenitor cells giving rise to the nucleus pulposus (NP) of the developing IVDs. Positive cells showed a membranous and/or cytoplasmic immunostaining, no reactivity was observed in the nuclear compartment. CD44 expression was always restricted to IVD precursor cells, whereas cartilage precursors were devoid of labelling. Conclusions: Our study shows, for the first time, that the stem cell marker CD44 selectively marks intervertebral disc progenitor cells, paralleling their differentiation toward a discogenic phenotype. Therefore, our results suggest that CD44 plays a key role in IVD development, allowing its differentiation from surrounding undifferentiated notochordal cells toward a IVD phenotype. Given the role of CD44 in IVD development, we may hypothesize that low CD44 levels might be associated with changes in IVD development and with susceptibility to develop back pain later in life