Consistency in scalable systems

[EN] While eventual consistency is the general consistency guarantee ensured in cloud environments, stronger guarantees are in fact achievable. We show how scalable and highly available systems can provide processor, causal, sequential and session consistency during normal functioning. Failures and network partitions negatively affect consistency and generate divergence. After the failure or the partition, reconciliation techniques allow the system to restore consistency.This work has been supported by EU FEDER and Spanish MICINN under research grants TIN2009-14460-C03-01 and TIN2010-17193.Ruiz Fuertes, MI.; Pallardó Lozoya, MR.; Muñoz-Escoí, FD. (2012). Consistency in scalable systems. En On the Move to Meaningful Internet Systems: OTM 2012. Springer Verlag (Germany). 7566:549-565. https://doi.org/10.1007/978-3-642-33615-7_7S5495657566Ahamad, M., Bazzi, R.A., John, R., Kohli, P., Neiger, G.: The power of processor consistency. 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Scalability approaches for causal multicast: a survey

The final publication is available at Springer via http://dx.doi.org/10.1007/s00607-015-0479-0Many distributed services need to be scalable: internet search, electronic commerce, e-government... In order to achieve scalability, high availability and fault tolerance, such applications rely on replicated components. Because of the dynamics of growth and volatility of customer markets, applications need to be hosted by adaptive, highly scalable systems. In particular, the scalability of the reliable multicast mechanisms used for supporting the consistency of replicas is of crucial importance. Reliable multicast might propagate updates in a pre-determined order (e.g., FIFO, total or causal). Since total order needs more communication rounds than causal order, the latter appears to be the preferable candidate for achieving multicast scalability, although the consistency guarantees based on causal order are weaker than those of total order. This paper provides a historical survey of different scalability approaches for reliable causal multicast protocols.This work was supported by European Regional Development Fund (FEDER) and Ministerio de Economia y Competitividad (MINECO) under research Grant TIN2012-37719-C03-01.Juan Marín, RD.; Decker, H.; Armendáriz Íñigo, JE.; Bernabeu Aubán, JM.; Muñoz Escoí, FD. (2016). Scalability approaches for causal multicast: a survey. Computing. 98(9):923-947. https://doi.org/10.1007/s00607-015-0479-0S923947989Adly N, Nagi M (1995) Maintaining causal order in large scale distributed systems using a logical hierarchy. In: IASTED Intnl Conf on Appl Inform, pp 214–219Aguilera MK, Chen W, Toueg S (1997) Heartbeat: a timeout-free failure detector for quiescent reliable communication. In: 11th Intnl Wshop on Distrib Alg (WDAG), Saarbrücken, pp 126–140Almeida JB, Almeida PS, Baquero C (2004) Bounded version vectors. 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Towards a standardization of biomethane potential tests

8 PáginasProduction of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced.The workshop in Leysin, Switzerland, has been financed by the Swiss Federal Office for Energy, and co-sponsored by Bioprocess Control Sweden AB, Lund, Sweden. The authors thank Alexandra Maria Murray for editing the English

Making Paths Explicit in the Scout Operating System

This paper makes a case for paths as an explicit abstraction in operating system design. Paths provide a unifying infrastructure for several OS mechanisms that have been introduced in the last several years, including fbufs, integrated layer processing, packet classifiers, code specialization, and migrating threads. This paper articulates the potential advantages of a path-based OS structure, describes the specific path architecture implemented in the Scout OS, and demonstrates the advantages in a particular application domain---receiving, decoding, and displaying MPEG-compressed video. 1 Introduction Layering is a fundamental structuring technique with a long history in system design. From early work on layered operating systems and network architectures [12, 32], to more recent advances in stackable systems [27, 15, 14, 26], layering has played a central role in managing complexity, isolating failure, and enhancing configurability. This paper describes a complementary, but equally f..

Protocol Latency: MIPS and Reality

This paper describes several techniques designed to improve protocol latency, and reports on their effectiveness when measured on a modern RISC processor---the DEC Alpha. We found that memory bandwidth---whichhas long been known to dominate network throughput---is also a key factor in protocol latency. The techniques are designed to increase the effectiveness of the instruction-cache and result in reduced processor stall rates. Department of Computer Science The University of Arizona Tucson, AZ 85721 1 This work supported in part by ARPA Contract DABT63-91-C-0030, by Digital Equipment Corporation. 1 Introduction Communication latency is often just as important as throughput in distributed systems [TL93], and for this reason, researchers have analyzed the latency characteristics of common network protocols like TCP/IP [KP93, CJRS89, Jac93]. These studies have shown that, despite the rich functionality offered by TCP/IP, the processing overheads are actually quite low. This paper rev..

Fast and general software solution to mutual exclusion on uniprocessors

This paper presents a technique to solve the mutual exclusion problem for uniprocessors purely in software. The idea is to execute atomic sequences without any hardware protection and, in the rare case that the atomic sequence is interrupted, to rollforward to the end of the sequence. The main contribution of this paper is to discuss the OS-related issues of this technique and to demonstrate its practicality, both in terms of flexibility and performance. It proposes a purely software-based technique that achieves mutual exclusion without any memory-accesses. Experiments show that this technique has the potential to outperform equivalent hardware mechanisms