Toward sustainable data centers: a comprehensive energy management strategy

Data centers are major contributors to the emission of carbon dioxide to the atmosphere, and this contribution is expected to increase in the following years. This has encouraged the development of techniques to reduce the energy consumption and the environmental footprint of data centers. Whereas some of these techniques have succeeded to reduce the energy consumption of the hardware equipment of data centers (including IT, cooling, and power supply systems), we claim that sustainable data centers will be only possible if the problem is faced by means of a holistic approach that includes not only the aforementioned techniques but also intelligent and unifying solutions that enable a synergistic and energy-aware management of data centers. In this paper, we propose a comprehensive strategy to reduce the carbon footprint of data centers that uses the energy as a driver of their management procedures. In addition, we present a holistic management architecture for sustainable data centers that implements the aforementioned strategy, and we propose design guidelines to accomplish each step of the proposed strategy, referring to related achievements and enumerating the main challenges that must be still solved.Peer ReviewedPostprint (author's final draft

La Salinització de la conca del Cardoner-Llobregat al Bages

Les aigües de la conca del Cardoner-Llobregat estan afectades per salinització, fins al punt de comprometre'n l'ús per a l'abastament a la conurbació de Barcelona. Les concentracions de clorurs (Cl?) superen àmpliament les recomanades en aigües destinades a la potabilització. La formació geològica salina Cardona i la seva explotació minera en diferents punts de la conca del Cardoner-Llobregat, a la comarca de Bages, indubtablement han d'estar relacionades amb la salinització de l'aigua. La presència de l'element potassi, extret a la superfície només per l'activitat minera, permet discriminar entre les filtracions d'aigua salada d'origen natural o geològic i les generades per la mineria. La distribució geogràfica de les principals surgències d'aigua salada i les seves proporcions relatives Cl-/K+ demostren que són els runams salins, les gegantines muntanyes estèrils on s'acumulen els residus de la mineria potàssica, l'origen de les majors aportacions actuals de sal als dos rius. Malgrat la salinització de les aigües, la mineria potàssica segueix fent créixer els runams salins del Bages en milers de tones al dia.Las aguas de la cuenca del Cardoner-Llobregat están afectadas por salinización, hasta el punto de comprometer su uso para el abastecimiento de la conurbación de Barcelona. Las concentraciones de cloruros (Cl-) superan ampliamente las recomendadas para aguas destinadas a la potabilización. La formación geológica Cardona y su explotación minera en diferentes puntos de la cuenca del Cardoner-Llobregat, en la comarca de Bages, indudablemente estarán relacionadas con la salinización del agua. La presencia del elemento potasio, extraído a la superfície sólo por la actividad minera, permite discriminar entre las filtraciones de agua salada de origen natural o geológico y las generadas por la minería. La distribución geográfica de los principales afloramientos de agua salada y sus proporciones relativas Cl-/K+ demuestran que las escombreras, las gigantescas montañas estériles donde se acumulan los residuos de la minería potásica, ocasionan las mayores aportaciones actuales de sal en los dos ríos. A pesar de la salinización de las aiguas, la escombreras de residuos salinos de la minería potásica en el Bages siguen creciendo al ritmo de miles de toneladas diarias.The salt content in the rivers Cardoner and Llobregat endangers its supply to the Barcelona area. The chloride (Cl-) concentration is much higher than the advised level for water for population supply purpose. The Cardona salt geological stratum and its potash mining activity in the Cardoner-Llobregat basin (Bages, Catalonia) certainly are related to the salt contamination. The presence of potassium, which is only in the land surface after mining, discriminates between natural from the geological layer or artificial from the mining activity brine sources. The geographical distribution of major brine sources, as well as their Cl-/K+ ratio, demonstrate that the giant, sterile mountains of salt residues from the mining activity contribute the most to the salt content of the two rivers at present. Despite their incidence in the water quality, the mountains of salt residues from the potash mining are still growing in thousands of tons daily

The lobby façace of Iberdrola Tower

p. 848-859The Iberdrola Tower in Bilbao, with its 165 m height, is planned to be finished during 2011. The building, designed by Pelli Clarke Pelli architects, will have the shape of a triangular prism with curved sides. The lobby façade will be entirely enclosed by a sculptural glass wall forming a softly rounded triangle in plan and supported by vertical glass fins. The design, simulation and testing of the glazed fins of the lobby façade will be discussed in the paper. Two different structural solutions for these elements will be compared, a plate girder and a lattice girder. The variable surface curvature of the façade will be achieved by means of cold-bend insulating glass units.Guitart, N.; Vila, J. (2010). The lobby façace of Iberdrola Tower. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/695

Fine-Grained Scheduling for Containerized HPC Workloads in Kubernetes Clusters

Containerization technology offers lightweight OS-level virtualization, and enables portability, reproducibility, and flexibility by packing applications with low performance overhead and low effort to maintain and scale them. Moreover, container orchestrators (e.g., Kubernetes) are widely used in the Cloud to manage large clusters running many containerized applications. However, scheduling policies that consider the performance nuances of containerized High Performance Computing (HPC) workloads have not been well-explored yet. This paper conducts fine-grained scheduling policies for containerized HPC workloads in Kubernetes clusters, focusing especially on partitioning each job into a suitable multi-container deployment according to the application profile. We implement our scheduling schemes on different layers of management (application and infrastructure), so that each component has its own focus and algorithms but still collaborates with others. Our results show that our fine-grained scheduling policies outperform baseline and baseline with CPU/memory affinity enabled policies, reducing the overall response time by 35% and 19%, respectively, and also improving the makespan by 34% and 11%, respectively. They also provide better usability and flexibility to specify HPC workloads than other comparable HPC Cloud frameworks, while providing better scheduling efficiency thanks to their multi-layered approach.Comment: HPCC202

Aprendizaje y enseñanza de las habilidades con patines

A partir del modelo conceptual que identifica las habilidades de los deportistas en función del entorno con el que interactúan, de los objetivos a alcanzar y de los instrumentos que se utilizan, se ha abordado el aprendizaje y la enseñanza de las habilidades básicas con patines. En las habilidades básicas, el equilibrio en el medio es esencial, pero los patines introducen variabilidad en la relación con el medio y, por lo tanto, dominar las habilidades con patines requiere un largo periodo de aprendizaje. Para acercarnos a la comprensión del aprendizaje de estas habilidades hemos entrevistado a practicantes expertos (skaters) y entrenadores de patinaje con experiencia en la iniciación del patinaje artístico y del hockey patines. A partir de las opiniones de los expertos, se pueden deducir algunas pautas para la enseñanza eficaz de las habilidades con patines

Performance characterization of containerization for HPC workloads on InfiniBand clusters: an empirical study

Containerization technology offers an appealing alternative for encapsulating and operating applications (and all their dependencies) without being constrained by the performance penalties of using Virtual Machines and, as a result, has got the interest of the High-Performance Computing (HPC) community to obtain fast, customized, portable, flexible, and reproducible deployments of their workloads. Previous work on this area has demonstrated that containerized HPC applications can exploit InfiniBand networks, but has ignored the potential of multi-container deployments which partition the processes that belong to each application into multiple containers in each host. Partitioning HPC applications has demonstrated to be useful when using virtual machines by constraining them to a single NUMA (Non-Uniform Memory Access) domain. This paper conducts a systematical study on the performance of multi-container deployments with different network fabrics and protocols, focusing especially on Infiniband networks. We analyze the impact of container granularity and its potential to exploit processor and memory affinity to improve applications’ performance. Our results show that default Singularity can achieve near bare-metal performance but does not support fine-grain multi-container deployments. Docker and Singularity-instance have similar behavior in terms of the performance of deployment schemes with different container granularity and affinity. This behavior differs for the several network fabrics and protocols, and depends as well on the application communication patterns and the message size. Moreover, deployments on Infiniband are also more impacted by the computation and memory allocation, and because of that, they can exploit the affinity better.We thank Lenovo for providing the testbed to run the experiments in this paper. This work was partially supported by Lenovo as part of Lenovo-BSC collaboration agreement, by the Spanish Government under contract PID2019-107255GB-C22, and by the Generalitat de Catalunya under contract 2017-SGR-1414 and under Grant No. 2020 FI-B 00257.Peer ReviewedPostprint (published version

Characterizing cloud federation for enhancing providers' profit

Cloud federation has been proposed as a new paradigm that allows providers to avoid the limitation of owning only a restricted amount of resources, which forces them to reject new customers when they have not enough local resources to fulfill their customers’ requirements. Federation allows a provider to dynamically outsource resources to other providers in response to demand variations. It also allows a provider that has underused resources to rent part of them to other providers. Both things could make the provider to get more profit when used adequately. This requires that the provider has a clear understanding of the potential of each federation decision, in order to choose the most convenient depending on the environment conditions. In this paper, we present a complete characterization of providers’ federation in the Cloud, including decision equations to outsource resources to other providers, rent free resources to other providers (i.e. insourcing), or shutdown unused nodes to save power, and we characterize these decisions as a function of several parameters. Then, we demonstrate in the evaluation section how a provider can enhance its profit by using these equations to exploit federation, and how the different parameters influence which is the best decision on each situation.Peer ReviewedPostprint (published version

Using resource-level information into nonadditive negotiation models for cloud market environments

Markets arise as an efficient way of organising resources in Cloud Computing scenarios. In Cloud Computing Markets, Brokers that represent both Clients and Service Providers meet in a Market and negotiate for the sales of resources or services. This paper defends the idea that efficient negotiations require of the usage of resource-level information for increasing the accuracy of negotiated Service Level Agreements and facilitating the achievement of both performance and business goals. A negotiation model based on the maximisation of nonadditive utility functions that considers multiple objectives is defined, and its validity is demonstrated in the experiments.Postprint (published version

Elastic management of tasks in virtualized environments

Nowadays, service providers in the Cloud offer complex services ready to be used as it was a commodity like water or electricity to their customers. A key technology for this approach is virtualization which facilitates provider's management and provides on-demand virtual environments, which are isolated and consolidated in order to achieve a better utilization of the provider's resources. However, dealing with some virtualization capabilities, such as the creation of virtual environments, implies an effort for the user in order to take benefit from them. In order to avoid this problem, we are contributing the research community with the EMOTIVE (Elastic Management of Tasks in Virtualized Environments) middleware, which allows executing tasks and providing virtualized environments to the users without any extra effort in an efficient way. This is a virtualized environment manager which aims to provide virtual machines that fulfils with the user requirements in terms of software and system capabilities. Furthermore, it supports fine-grained local resource management and provides facilities for developing scheduling policies such as migration and checkpointing.Postprint (published version

Maximising revenue in cloud computing markets by means of economically enhanced SLA management

This paper proposes a bidirectional communication between market brokers and resource managers in Cloud Computing Markets. This communication is implemented by means of an Economically Enhanced Resource Manager (EERM), that supports the negotiation process by deciding which tasks can be allocated or not, and under which economic and technical conditions. The EERM also uses the economic information that collects from market layers to manage the resources accordingly to concrete BLOs. This paper shows several Business Policies and Rules for maximizing the revenue of a Cloud Provider that sells its services and resources in a market. Their validity is demonstrated through several experiments that shown how the application of these rules can have a positive influence in the revenue and minimize the violations of Service-Level Agreements.Preprin