On the Communication Cost of MDS Erasure Codes in Distributed Storage Systems

Distributed storage systems store some redundant data to keep the degree of availability of the stored data constant and also to increase the system's resistance against failures. This type of systems usually use pure replication or methods based on RAID systems as redundancy schemes. In this paper, we study the communication cost of a distributed data storage system using Maximum Distance Separable (MDS) erasure codes. Our focus is reduction of the cost of one-to-many communication used in data reconstruction/repair initialization and update operations. We propose the use of two different communication approaches on the area of distributed storage systems for the above operations; Steiner tree approach and multi-shortest path approach. We also analyse these two communication approaches empirically and theoretically. Our theoretical results indicate that Steiner tree approach has lower message usage, whereas, multi-shortest path approach has lower time usage for data reconstruction/repair initialization operations. On the other hand, Steiner tree approach has better message and time metrics for the data update process. Furthermore, our experimental results support these theoretical results. Thus, users can choose between the two approaches depending on their needs and priorities

Homomorphic Minimum Bandwidth Repairing Codes

28th International Symposium on Computer and Information Sciences (ISCIS) -- OCT 28-29, 2013 -- Inst Henri Poincare, Paris, FRANCEWOS: 000333692000033To store data reliably, a number of coding schemes including Exact-Minimum Bandwidth Regenerating codes (exact-MBR) and Homomorphic Self Repairing Codes (HSRC) exist. Exact-MBR offers minimum bandwidth usage whereas HSRC has low computational overhead in node repair. We propose a new hybrid scheme, Homomorphic Minimum Bandwidth Repairing Codes, derived from the above coding schemes. Our coding scheme provides two options for node repair operation. The first option offers to repair a node using minimum bandwidth and higher computational complexity while the second one repairs a node using fewer nodes, lower computational complexity and higher bandwidth. In addition, our scheme introduces a basic integrity checking mechanism

Enumerating Possible Seedings in a Knockout Tournament

5th International Conference on Computer Science and Engineering (UBMK) -- SEP 09-11, 2020 -- Diyarbakir, TURKEYWOS:000629055500044A knockout tournament, also known as an elimination tournament is a very common competition scheme where competitors play a one-versus-one game with the loser eliminated from the competition and the winner advancing to the next round until there is only one competitor left. The setting of the first round of games called "seeding" naturally influences the competition. Although there is considerable amount of work in the literature on how to seed a knockout tournament to achieve some objectives, an algorithm to enumerate possible knockout tournament seedings has not been explicitly presented to the best of our knowledge. in this paper, a discussion on counting the number of possible seedings in a knockout tournament and an algorithm for effectively enumerating the seedings are proposed.IEEE Turkey Sect, Istanbul Teknik Univ, Gazi Univ, Atilim Univ, Dicle Univ, Turkiye Bilisim Vakfi, Kocaeli UnivScientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)Can Atilgan would like to thank the Scientific and Technological Research Council of Turkey (TUBITAK) for their financial support during his PhD studies

Managing TCP Connections of File Reconstruction Process in Erasure Codes

23nd Signal Processing and Communications Applications Conference (SIU) -- MAY 16-19, 2015 -- Inonu Univ, Malatya, TURKEYWOS: 000380500900455In this paper, we propose a new method for reducing the elapsed time and the number of messages used in the data reconstruction process of distributed storage systems based on erasure codes through managing TCP connections in case of congestion. The data reconstruction process using the new method and one not using such management of TCP connections are both implemented in the network simulation environment. According to the simulation results, the new method requires less time and fewer messages for data reconstruction in case of congestion as compared to the data reconstruction process without such control frame.Dept Comp Engn & Elect & Elect Engn, Elect & Elect Engn, Bilkent Uni

A 2-hop Coloring-Based Collision Free Infrastructure Design for Wireless Sensor Networks

13th HONET-ICT International Symposium on Smart MicroGrids for Sustainable Energy Sources enabled by Photonics and IoT Sensors -- OCT 13-14, 2016 -- Nicosia, CYPRUSWOS: 000391440600011This paper mainly proposes a design for a communication infrastructure for Wireless Sensor Networks. The proposed design prevents message collisions by arranging the time schedules to send, receive, forward and overhear packets of the nodes considering 2-hop graph coloring mechanism. The system aims to exclude the compromised nodes in the network using the overhearing mechanism, and copes with recovering the paths of the legitimate nodes using multipath redundancy. The proposed scheduling-based and overhearing supported infrastructure brings the advantage of providing the Sensor Networks with both reliable communication using backup paths and energy conservation by preventing the collisions.HONET ICT, IEEE Commun Soc, IEEE, UCCTEA Chamber Elect Engineers, CYPRUS Int Univ, UNC CHARLOTT

A simple shuffle-based stable in-place merge algorithm

1st World Conference on Information Technology (WCIT) -- OCT 06-10, 2010 -- Bahcesehir Univ, Istanbul, TURKEYWOS: 000299159800170Sorting is one of the most fundamental problems in computer science. Divide-and-conquer based sorting algorithms use successive merging to combine sorted arrays; therefore performance of merging is critical for these types of applications. The classic merge algorithm uses an extra O(m+n) memory for combining arrays of size m and n. Some improvements on merge algorithms include in-place methods which reduce or eliminate additional memory space, thus getting more practical value. We present a new in-place, stable and shuffle-based merge algorithm which is simple to understand and program. The algorithm starts applying perfect shuffle on two sorted arrays. Then, using the knowledge that odd and even-indexed numbers are sorted among themselves, comparisons are made and then misplaced elements are relocated by applying successive inverse perfect shuffle and swap operations on blocks. We have implemented and compared the new algorithm with the classical merge algorithm and the shuffle-based algorithm of Ellis and Markov (Comp. J. 1(2000)). Through experiments we have observed that the new algorithm exhibits linear run time behaviour and has dramatic performance improvement compared to the Ellis and Markov's algorithm [1]. (C) 2010 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Guest Editor

Parallelization of network motif discovery using star contraction

WOS:000614249000006Network motifs are widely used to uncover structural design principles of complex networks. Current sequential network motif discovery algorithms become inefficient as motif size grows, thus parallelization methods have been proposed in the literature. in this study, we use star contraction algorithm to partition complex networks efficiently for parallel discovery of network motifs. We propose two new heuristics to make star contraction more suitable for partitioning of complex networks. The effectiveness of our partitioning strategies is verified using the ESU algorithm for subgraph counting. We also propose a ghost vertices detection algorithm to ensure that all the motifs located in multiple parts are exactly found. We implement our method using MPI libraries and tested on real-life complex networks of different domains. We compared speedups of star contraction algorithm with speedups of other graph partitioning algorithms. Our algorithm obtained better speedups than those of other partitioning algorithms for most cases. Our algorithm provides significant speedups when compared to sequential ESU algorithm allowing discovery of larger network motifs.TUBITAK BIDEB-2211 National Scholarship Programme for PhD StudentsTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)We thank the anonymous reviewers for their helpful comments. Esra R. Ateskan acknowledges the financial support of TUBITAK BIDEB-2211 National Scholarship Programme for PhD Students. The computational tests performed at TUBITAK ULAKBIM, High Performance and Grid Computing Center