Leveraging workload knowledge to design data center networks

Data center networks are at the heart of cloud infrastructure. They allow cloud workloads to scale, be flexible, and meet the needs of modern businesses. Since the demand for higher bandwidth, lower latency, and minimal resource cost, is growing, cloud providers must continuously improve the efficiency of their infrastructure. The key to achieving optimal performance of data center networks is to understand the communication needs and behavior of modern cloud workloads. Intuitively, as cloud operators collect more knowledge about their tenants and applications, i.e., obtain workload specifications like required bandwidth, tail latency requirements, time to first byte, etc., they can use that knowledge to precisely provision the physical network infrastructure and deploy sophisticated control algorithms that maximize performance, increase utilization, and reduce the cost of cloud resources. However, obtaining and leveraging workload specifications is challenging in practice. On the one hand, users do not have clear incentives in terms of performance and cost benefits to invest the effort and help obtain the specifications of their workloads. On the other hand, cloud operators cannot provide those benefits without having a substantial number of workload specifications. Thus, many proposed systems that depend on application-specific knowledge remain in the domain of academic research, despite their significant performance advantages. To break this vicious circle, we propose a set of methods, theoretical results, and systems that enhance the process of obtaining and using workload specifications in the data center network environment. Moreover, we demonstrate how to explore and utilize the space of various workload specifications. We start the exploration from coarse-grained insights from the past execution of cloud workloads and demonstrate how they can be used to reduce the cost of physical network infrastructure. Our system, Iris, leverages historical knowledge to reduce the overall cost of one of the most expensive parts of cloud networks -- Data Center Interconnect (DCI) -- by an order of magnitude compared to equivalent workload-agnostic solutions. Furthermore, we analyze how to obtain fine-grained workload specifications that describe the future behavior of cloud applications and use them to enhance network efficiency. Thanks to our system, Flux, we automatically infer advance specifications using machine learning methods. Then, we show how to leverage these specification estimates to deploy sophisticated network control and scheduling mechanisms that achieve an order of magnitude improvement in terms of flow completion time and queue occupancy compared to the systems deployed in the cloud today. Finally, we provide a set of rules and guidelines that cloud providers need to satisfy in order to motivate tenants to collaborate in the process of obtaining and utilizing workload specifications, and ultimately, make these specification-dependant systems practical in the modern cloud environment

Variability of Norway spruce morphometric characteristics in progeny tests in Bosnia and Herzegovina

U radu su prikazani rezultati analize morfometrijskih karakteristika sadnica smrče u testovima potomstva na području BiH, sa lokaliteta: Drinić i Srebrenica. Testovi potomstva osnovani su od sadnica koje vode porijeklo iz šest prirodnih populacija iz BiH. Mjerena je ukupna visina sadnica, prečnik korijenovog vrata, te udaljenost pršljenova od zemljišta što predstavlja visine koje su sadnice dostigle u 2011, 2012, 2013. i 2014. godini. Dobijeni rezultati ukazuju na statistički značajne razlike između analiziranih karakteristika posmatranih populacija. Posebno se izdvajaju populacije Potoci i Olovo, koje su u oba testa potomstva imale najveći prirast tokom posmatranog perioda. Uticaj suše tokom 2013. godine uočava se u testu potomstva u Srebrenici, pri čemu je prirast tokom 2013. godine manji od prirasta u 2012. godini za više od 50%. Uticaj suše u testu potomstva u Driniću se ne uočava. Istraživanja daju polazne osnove u selekcionisanju polaznih populacija, a kao glavni cilj postavlja se brz porast sadnica.The paper presents the results of an analysis of morphometric characteristics of Norway spruce seedlings in the progeny tests in Bosnia and Herzegovina, localities: Drinić and Srebrenica. Progeny tests were established by using seedlings originating from six natural populations from Bosnia and Herzegovina. Seedling height, root collar and whorl distance from the ground, which represents seedling heights in 2011, 2012 and 2013 were measured. The results indicate statistically significant differences between the analyzed characteristics of the observed population. Especially interesting are the populations Potoci and Olovo, which showed the highest growth during the observed period in both progeny tests. The impact of the drought in 2013 can be seen in the progeny test in Srebrenica where height growth in 2013 was lower by more than 50% in comparison to 2012. The impact of drought in the progeny test in Drinić was not observed. The research provides the baseline when selecting the starting population, where the rapid growth of seedlings is set as the main goal

Gap-phase dynamics in the old-growth forest of Lom, Bosnia and Herzegovina

We investigated forest canopy gaps in the mixed beech (Fagus sylvatica L.), silver fir (Abies alba Miller), and Norway spruce (Picea abies (L.) Karst.) old-growth forest of Lom in the Dinaric Mountains of Bosnia and Herzegovina. Gap size, age, gap fraction, gapmaker characteristics and the structure and composition of gapfillers were documented to investigate gap dynamics. The percentages of forest area in canopy and expanded gaps were 19% and 41%, respectively. The median canopy gap size was 77 m, and ranged from 11 to 708 m. Although there were many single tree-fall gaps, the majority had multiple gapmakers that were often in different stages of decay, suggesting gap expansion is important at the study site. Of the gapmakers recorded, 14% were uprooted stems, 60% snapped stems, and 26% were standing dead trees. Dendroecological analysis suggests that gap formation varied in time. The density of gapfillers was not correlated to gap size, and the species composition of gapfillers varied between seedling, sapling, and tree life stages. The results suggest that gaps are mainly formed by endogenous senescence of single canopy trees. Exogenous disturbance agents, most likely related to wind and snow, act mainly as secondary agents in breaking weakened trees and in expanding previously established gaps. Although the findings are partially consistent with other studies of gap disturbance processes in similar old-growth forests in central Europe, the observed gap dynamic places the Lom core area at the end of a gradient that ranges from forests controlled by very small-scale processes to those where large, stand replacing disturbances predominate.22</ja:p

Gap-phase dynamics in the old-growth forest of Lom, Bosnia and Herzegovina

We investigated forest canopy gaps in the mixed beech (Fagus sylvatica L.), silver fir (Abies alba Miller), and Norway spruce (Picea abies (L.) Karst.) old-growth forest of Lom in the Dinaric Mountains of Bosnia and Herzegovina. Gap size, age, gap fraction, gapmaker characteristics and the structure and composition of gapfillers were documented to investigate gap dynamics. The percentages of forest area in canopy and expanded gaps were 19% and 41%, respectively. The median canopy gap size was 77 m, and ranged from 11 to 708 m. Although there were many single tree-fall gaps, the majority had multiple gapmakers that were often in different stages of decay, suggesting gap expansion is important at the study site. Of the gapmakers recorded, 14% were uprooted stems, 60% snapped stems, and 26% were standing dead trees. Dendroecological analysis suggests that gap formation varied in time. The density of gapfillers was not correlated to gap size, and the species composition of gapfillers varied between seedling, sapling, and tree life stages. The results suggest that gaps are mainly formed by endogenous senescence of single canopy trees. Exogenous disturbance agents, most likely related to wind and snow, act mainly as secondary agents in breaking weakened trees and in expanding previously established gaps. Although the findings are partially consistent with other studies of gap disturbance processes in similar old-growth forests in central Europe, the observed gap dynamic places the Lom core area at the end of a gradient that ranges from forests controlled by very small-scale processes to those where large, stand replacing disturbances predominate.2

Correlation of Non-Invasive Transthoracic Doppler Echocardiography with Invasive Doppler Wire-Derived Coronary Flow Reserve and Their Impact on Infarct Size in Patients with ST-Segment Elevation Myocardial Infarction Treated with Primary Percutaneous Coronary Intervention

Background: Coronary microvascular dysfunction is associated with adverse prognosis after ST-segment elevation myocardial infarction (STEMI). We aimed to compare the invasive, Doppler wire-based coronary flow reserve (CFR) with the non-invasive transthoracic Doppler echocardiography (TTDE)-derived CFR, and their ability to predict infarct size. Methods: We included 36 patients with invasive Doppler wire assessment on days 3&ndash;7 after STEMI treated with primary percutaneous coronary intervention (PCI), of which TTDE-derived CFR was measured in 47 vessels (29 patients) within 6 h of the invasive Doppler. Infarct size was assessed by cardiac magnetic resonance at a median of 8 months. Results: The correlation between invasive and non-invasive CFR was modest in the overall cohort (rho 0.400, p = 0.005). It improved when only measurements in the LAD artery were considered (rho 0.554, p = 0.002), with no significant correlation in the RCA artery (rho &minus;0.190, p = 0.435). Both invasive (AUC 0.888) and non-invasive (AUC 0.868) CFR, measured in the recanalized culprit artery, showed a good ability to predict infarct sizes &ge;18% of the left ventricular mass, with the optimal cut off values of 1.85 and 1.80, respectively. Conclusions: In patients with STEMI, TTDE- and Doppler wire-derived CFR exhibit significant correlation, when measured in the LAD artery, and both have a similarly strong association with the final infarct size

A comprehensive quality control system suitable for academic research: application in a pediatric study

Aim: Clinical research in pediatrics is progressively initiated by academia. As the reliability of pharmacodynamic measures is closely linked to the quality of bioanalytical data, bioanalytical quality assurance is crucial. However, clear guidance on comprehensive bioanalytical quality monitoring in the academic environment is lacking. Methods &amp; results: By applying regulatory guidelines, international recommendations and scientific discussions, a five-step quality control system for monitoring the bioanalysis of aldosterone by immunoassay was developed. It comprised performance qualification, calibration curve evaluation, analysis of the intra- and inter-run performance via quality control samples, incurred sample reanalysis and external quality assessment by interlaboratory testing. A total of 55 out of 70 runs were qualified for the quantification of aldosterone in the study sample enabling the evaluation of 954 pediatric samples and demonstrating reliability over the 29-month bioanalysis period. Conclusion: The bioanalytical quality control system successfully monitored the aldosterone assay performance and proved its applicability in the academic environment. </jats:p