Computing the probability for data loss in two-dimensional parity RAIDs

Parity RAIDs are used to protect storage systems against disk failures. The idea is to add redundancy to the system by storing the parity of subsets of disks on extra parity disks. A simple two-dimensional scheme is the one in which the data disks are arranged in a rectangular grid, and every row and column is extended by one disk which stores the parity of it. In this paper we describe several two-dimensional parity RAIDs and analyse, for each of them, the probability for data loss given that f random disks fail. This probability can be used to determine the overall probability using the model of Hafner and Rao. We reduce subsets of the forest counting problem to the different cases and show that the generalised problem is #Phard. Further we adapt an exact algorithm by Stones for some of the problems whose worst-case runtime is exponential, but which is very efficient for small fixed f and thus sufficient for all real-world applications

Entwicklung bionischer Stützstrukturen im Bereich der additiven Fertigung

In dieser Arbeit werden Ans¨atze fu¨r Stu¨tzstrukturen in der additiven Fertigung entwi- ckelt. Diese sollen im selektiven Laserschmelzen eingesetzt werden, wo sie die herk¨omm- lichen Strukturen im verbauten und damit verschwendeten Material ersetzen und damit die Bauzeit beziehungsweise die Produktionsdauer verkürzen. Hierfür werden Modelle an Strukturen simuliert, die auf einer bionischen Herleitung basieren und sowohl mit herkömmlichen als auch technisch hergeleiteten Stützstrukturen verglichen. Für die Arbeit wird ein Fokus auf den metallischen Werkstoff TiAl6V4 gelegt, der durch Branchen wie der Luft-und Raumfahrt, Automobil oder Medizintechnik Verwendung findet. Der Fertigungsprozess wird mittels den Daten einer ConceptLaser M2 (Maschine zur Her- stellung von selektive lasergeschmolzenen Werkstücken) simuliert und die Ergebnisse nach Ablösen von der Bauplattform verglichen. Anschließend wird der auftretende Ver- zug in Abhäangigkeit von dem verbauten Volumen betrachtet, um Ruückschlüsse über die mögliche Verbesserung zu ziehen

Sport and leisure-time physical activity over the life course

It is desirable to get as many people as possible to engage in long-term leisure-time physical activity (LTPA) due to the health-enhancing effects. Although the proportion of individuals who are physically active in their leisure time appears to have increased in Switzerland in the past years (e.g., Lamprecht et al., 2020), little is known so far about the dynamic of change in LTPA trajectories over the life course. LTPA trajectories of 1,456 Swiss resi- dents aged 35 to 76 years (random sampling) were reconstructed with the help of a retrospective telephone interview (CATI method). To address the dif- ficulties of retrospective data collection, the article presents the careful development of the questionnaire on the basis of current evidence. The majority of the respondents (approx. 73%) show a long-term LTPA without dropout (dropout = LTPA less than once a week over one year and longer), only a minority of whom (approx. 18%) took up their LTPA after the age of 20. In addition, there is also a group with a somewhat unstable LTPA trajectory (approx. 24%) that includes at least one dropout. For members of the latter group, the longer the inactive episode lasted, the lower were their chances of entering an LTPA. While the different LTPA trajectory groups differed only slightly with regard to socioeconomic characteristics, analyses of their sport- and physical activity-related history reveal that self-organized LTPA in child- hood and youth may be seen as a success factor for lifelong LTPA. The pro- portion of people practicing (long-term) LTPA is presumably overrepresented in the sample. This limitation should be taken into account, but analyses of possible advantageous conditions of long-term or lifelong LTPA are neverthe- less possible. The results indicate a demand for more specific theories related to the causality behind the observable LTPA behavio

Evaluation of SLA-based decision strategies for VM scheduling in cloud data centers

Copyright © 2016 held by owner/author(s). Service level agreements (SLAs) gain more and more importance in the area of cloud computing. An SLA is a contract between a customer and a cloud service provider (CSP) in which the CSP guarantees functional and non-functional quality of service parameters for cloud services. Since CSPs have to pay for the hardware used as well as penalties for violating SLAs, they are eager to fulfill these agreements while at the same time optimizing the utilization of their resources. In this paper we examine SLA-aware VM scheduling strategies for cloud data centers. The service level objectives considered are resource usage and availability. The sample resources are CPU and RAM. They can be overprovisioned by the CSPs which is the main leverage to increase their revenue. The availability of a VM is affected by migrating it within and between data centers. To get realistic results, we simulate the effect of the strategies using the FederatedCloudSim framework and real-world workload traces of business-critical VMs. Our evaluation shows that there are considerable differences between the scheduling strategies in terms of SLA violations and the number of migrations. From all strategies considered, the combination of the Minimization of Migrations strategy for VM selection and the Worst Fit strategy for host selection achieves the best results

And now for something completely different: running Lisp on GPUs

The internal parallelism of compute resources increases permanently, and graphics processing units (GPUs) and other accelerators have been gaining importance in many domains. Researchers from life science, bioinformatics or artificial intelligence, for example, use GPUs to accelerate their computations. However, languages typically used in some of these disciplines often do not benefit from the technical developments because they cannot be executed natively on GPUs. Instead existing programs must be rewritten in other, less dynamic programming languages. On the other hand, the gap in programming features between accelerators and common CPUs shrinks permanently. Since accelerators are becoming more competitive with regard to general computations, they will not be mere special-purpose processors in the future. It is a valid assumption that future GPU generations can be used in a similar or even the same way as CPUs and that compilers or interpreters will be needed for a wider range of computer languages. We present CuLi, an interactive Lisp interpreter, that performs all computations on a CUDA-capable GPU. The host system is needed only for the input and the output. At the moment, Lisp programs running on CPUs outperform Lisp programs on GPUs, but we present trends indicating that this might change in the future. Our study gives an outlook on the possibility of running Lisp programs or other dynamic programming languages on next-generation accelerators

Computing the Probability for Data Loss in Two-Dimensional Parity RAIDs

Parity RAIDs are used to protect storage systems against disk failures. The idea is to add redundancy to the system by storing the parity of subsets of disks on extra parity disks. A simple two-dimensional scheme is the one in which the data disks are arranged in a rectangular grid, and every row and column is extended by one disk which stores the parity of it. In this paper we describe several two-dimensional parity RAIDs and analyse, for each of them, the probability for data loss given that f random disks fail. This probability can be used to determine the overall probability using the model of Hafner and Rao. We reduce subsets of the forest counting problem to the different cases and show that the generalised problem is #Phard. Further we adapt an exact algorithm by Stones for some of the problems whose worst-case runtime is exponential, but which is very efficient for small fixed f and thus sufficient for all real-world applications

An activity-based and dynamic approach to calculate road traffic noise damages

In this paper, an activity-based and dynamic approach is presented to analyze population exposures to road traffic noise. The contribution of this innovative approach is that (1) affected people at the workplace and places of education are incorporated and (2) the within day dynamics of varying population densities in different areas of the city is explicitly taken into account. The proposed methodology is applied to a real-world case study of the Greater Berlin area. The results demonstrate the need to account for the spatial and temporal variation in the population since the use of static resident numbers would result in an overestimation of residential noise damages. Going beyond residential exposures, the inclusion of further activity types is found to have a substantial effect on the results. Assuming individuals at work or education to be additionally affected by noise, population exposures in the central business districts are much larger than in residential areas. The proposed approach may be seen as a first step towards improved noise mapping standards to provide better recommendations for policy makers and ensure a more efficient use of noise control strategies

Human Aging Magnifies Genetic Effects on Executive Functioning and Working Memory

We demonstrate that common genetic polymorphisms contribute to the increasing heterogeneity of cognitive functioning in old age. We assess two common Val/Met polymorphisms, one affecting the Catechol-O-Methyltransferase (COMT) enzyme, which degrades dopamine (DA) in prefrontal cortex (PFC), and the other influencing the brain-derived neurotrophic factor (BDNF) protein. In two tasks (Wisconsin Card Sorting and spatial working memory), we find that effects of COMT genotype on cognitive performance are magnified in old age and modulated by BDNF genotype. Older COMT Val homozygotes showed particularly low levels of performance if they were also BDNF Met carriers. The age-associated magnification of COMT gene effects provides novel information on the inverted U-shaped relation linking dopaminergic neuromodulation in PFC to cognitive performance. The modulation of COMT effects by BDNF extends recent evidence of close interactions between frontal and medial-temporal circuitries in executive functioning and working memory