Schweizerisches Wirtschaftsarchiv, Basel

Bestandesübersicht des Schweizerischen Wirtschaftsarchivs in Basel

Group communications and database replication:techniques, issues and performance

Databases are an important part of today's IT infrastructure: both companies and state institutions rely on database systems to store most of their important data. As we are more and more dependent on database systems, securing this key facility is now a priority. Because of this, research on fault-tolerant database systems is of increasing importance. One way to ensure the fault-tolerance of a system is by replicating it. Replication is a natural way to deal with failures: if one copy is not available, we use another one. However implementing consistent replication is not easy. Database replication is hardly a new area of research: the first papers on the subject are more than twenty years old. Yet how to build an efficient, consistent replicated database is still an open research question. Recently, a new approach to solve this problem has been proposed. The idea is to rely on some communication infrastructure called group communications. This infrastructure offers some high-level primitives that can help in the design and the implementation of a replicated database. While promising, this approach to database replication is still in its infancy. This thesis focuses on group communication-based database replication and strives to give an overall understanding of this topic. This thesis has three major contributions. In the structural domain, it introduces a classification of replication techniques. In the qualitative domain, an analysis of fault-tolerance semantics is proposed. Finally, in the quantitative domain, a performance evaluation of group communication-based database replication is presented. The classification gives an overview of the different means to implement database replication. Techniques described in the literature are sorted using this classification. The classification highlights structural similarities of techniques originating from different communities (database community and distributed system community). For each category of the classification, we also analyse the requirements imposed on the database component and group communication primitives that are needed to enforce consistency. Group communication-based database replication implies building a system from two different components: a database system and a group communication system. Fault-tolerance is an end-to-end property: a system built from two components tends to be as fault-tolerant as the weakest component. The analysis of fault-tolerance semantics show what fault-tolerance guarantee is ensured by group communication based replication techniques. Additionally a new faulttolerance guarantee, group-safety, is proposed. Group-safety is better suited to group communication-based database replication. We also show that group-safe replication techniques can offer improved performance. Finally, the performance evaluation offers a quantitative view of group communication based replication techniques. The performance of group communication techniques and classical database replication techniques is compared. The way those different techniques react to different loads is explored. Some optimisation of group communication techniques are also described and their performance benefits evaluated

Comparison of Database Replication Techniques Based on Total Order Broadcast

In this paper, we present a performance comparison of database replication techniques based on total order broadcast. While the performance of total order broadcast-based replication techniques has been studied in previous papers, this paper presents many new contributions. First, it compares with each other techniques that were presented and evaluated separately, usually by comparing them to a classical replication scheme like distributed locking. Second, the evaluation is done using a finer network model than previous studies. Third, the paper compares techniques that offer the same consistency criterion (one-copy serializability) in the same environment using the same settings. The paper shows that, while networking performance has little influence in a LAN setting, the cost of synchronizing replicas is quite high. Because of this, total order broadcast-based techniques are very promising as they minimize synchronization between replicas

Using simulated fluorescence cell micrographs for the evaluation of cell image segmentation algorithms

The zip archive contains real images showing macrophages. (ZIP 28979 kb

Simulated movies of fluorescently stained bacteria

Wiesmann V, Bergler M, Münzenmayer C, Wittenberg T. Simulated movies of fluorescently stained bacteria. Fraunhofer Institute for Integrated Circuits, Erlangen, Germany; 2017.Simulated biomovies of fluorescent cells were created by employing cell simulation based on shape, texture, growth and motion information. They are depicted in fluorescent channels where noise and other artifacts were additionally modeled. While the original cell simulation software (Wiesmann et al. 2013) has been extended for biomovie simulation, the step for bacterial growth simulation is similar to image simulation. First, the cell shape is calculated. Second, the cell position on the image grid is calculated. Third, the cell texture is added. Fourth and last, imaging artifacts and noise are added to the final image

Using Optimistic Atomic Broadcast in Transaction Processing Systems

Atomic broadcast primitives are often proposed as a mechanism to allow fault-tolerant cooperation between sites in a distributed system. Unfortunately, the delay incurred before a message can be delivered makes it difficult to implement high performance, scalable applications on top of atomic broadcast primitives. Recently, a new approach has been proposed for atomic broadcast which, based on optimistic assumptions about the communication system, reduces the average delay for message delivery to the application. In this paper, we develop this idea further and show how applications can take even more advantage of the optimistic assumption by overlapping the coordination phase of the atomic broadcast algorithm with the processing of delivered messages. In particular, we present a replicated database architecture that employs the new atomic broadcast primitive in such a way that communication and transaction processing are fully overlapped, providing high performance without relaxing transaction correctness

Superconductivity at 5.4 K in β\beta-Bi2_2Pd

We investigate bulk superconductivity in a high-quality single crystal of Bi$_2$Pd ($\beta$-Bi$_2$Pd, space group; I4/mmm) at temperatures less than 5.4 K by exploring its electrical resistivity, magnetic susceptibility, and specific heat. The temperature dependence of the electrical resistivity shows convex-upward behaviors at temperatures greater than 40-50 K, which can be explained by a parallel-resistor model. In addition, we demonstrate that this material is a multiple-band/multiple-gap superconductor based on the temperature dependences of the specific heat and the upper critical field.Comment: 4 pages, 3 figure

Mode, Macht & Marketing : Propaganda-Aktivitäten der Basler Seidenbandfabrikanten anfangs des 20. Jahrhunderts : eine Ausstellung zum 100jährigen Jubiläum

Immer wieder ist es dem Schweizerischen Wirtschaftsarchiv (SWA) in seiner 100jährigen Geschichte gelungen, wertvolle Akten von Verbänden und Firmen zu übernehmen und sie damit vor der Vernichtung zu bewahren. Auch der Bestand des Basler Bandpropaganda- Comités gehört dazu. Mit der Ausstellung und der hier vorliegenden Begleitpublikation möchten wir auf unser Anliegen aufmerksam machen, historische Firmen- und Verbandsarchive als Kulturgut wahrzunehmen. Die Akten des Comités geben Einblick in eine Marketingkampagne zu Gunsten des Bandes, die geheim ablaufen sollte und mit subtiler Beein- flussung der Modistinnen und des Publikums zu arbeiten versuchte. Die prächtigen Fotografien, die farbenfrohen Musterbücher und Objekte aus Seidenband erfreuen unser Auge und lassen uns in die Modewelt des beginnenden 20. Jahrhunderts eintauchen. Nicht zuletzt erzählen uns die Archivalien von der einst so bedeutenden Seidenbandindustrie, die um 1930 rasant an Bedeutung verlor. Zum hundertsten Geburtstag war es dem SWA ein Anliegen, einige Trouvaillen aus den Archivschachteln herauszuholen und sie in kompakter und infor- mativer Form einem breiten Publikum vorzustellen