A reliability model for dependent and distributed MDS disk array units

Archiving and systematic backup of large digital data generates a quick demand for multi-petabyte scale storage systems. As drive capacities continue to grow beyond the few terabytes range to address the demands of today’s cloud, the likelihood of having multiple/simultaneous disk failures became a reality. Among the main factors causing catastrophic system failures, correlated disk failures and the network bandwidth are reported to be the two common source of performance degradation. The emerging trend is to use efficient/sophisticated erasure codes (EC) equipped with multiple parities and efficient repairs in order to meet the reliability/bandwidth requirements. It is known that mean time to failure and repair rates reported by the disk manufacturers cannot capture life-cycle patterns of distributed storage systems. In this study, we develop failure models based on generalized Markov chains that can accurately capture correlated performance degradations with multiparity protection schemes based on modern maximum distance separable EC. Furthermore, we use the proposed model in a distributed storage scenario to quantify two example use cases: Primarily, the common sense that adding more parity disks are only meaningful if we have a decent decorrelation between the failure domains of storage systems and the reliability of generic multiple single-dimensional EC protected storage systems.WOS:000460728600008Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ1 - Q2ArticleUluslararası işbirliği ile yapılmayan - HAYIRMart2019YÖK - 2018-1

Founsure 1.0: An erasure code library with efficient repair and update features

Founsure is an open-source software library that implements a multi-dimensional graph-based erasure coding entirely based on fast exclusive OR (XOR) logic. Its implementation utilizes compiler optimizations and multi-threading to generate the right assembly code for the given multi-core CPU architecture with vector processing capabilities. Founsure possesses important features that shall find various applications in modern data storage, communication, and networked computer systems, in which the data needs protection against device, hardware, and node failures. As data size reached unprecedented levels, these systems have become hungry for network bandwidth, computational resources, and average consumed power. To address that, the proposed library provides a three-dimensional design space that trades off the computational complexity, coding overhead, and data/node repair bandwidth to meet different requirements of modern distributed data storage and processing systems. Founsure library enables efficient encoding, decoding, repairs/rebuilds, and updates while all the required data storage and computations are distributed across the network nodes.Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) Grant Number : 115C111 - 119E235WOS:000656825700019Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ3ArticleUluslararası işbirliği ile yapılmayan - HAYIRJanuary2021YÖK - 2020-2

Çoklu–süreçli ortamlarda silme kodlama yöntemleri’nin çoklu–dizin uygulaması

Şefik Şuayb Arslan (MEF Author)Galois alan aritmetiği depolama ve iletişim cihazlarını veri kayıplarına karşı korumak için Reed-Solomon silme kodlarının temelini oluşturmaktadır. Galois alan aritmeti^ginin en güncel uygulamaları hızlı Galois alan hesaplamaları yapmamıza imkan sağlayan Intel’in SIMD eklerinde olduğu gibi 128-bitlik işlemci vektör talimatlarına dayanmaktadır. Buna rağmen, bu uygulamalar çoklu–dizin ve çoklu–süreçli ortamlara göre optimize edilmemiştir. Diğer taraftan, sunucuların çoklu istekleri eş zamanlı olarak yerine getirmesi ve donanımın sağladığı tüm paralelliği kodlama yükünü etkili yürütmek için kullanması arzu edilmektedir. Bu makale silme kodlarının çoklu-dizin işlemcilerle çoklu–süreçli ortamlarda nasıl kullanılaca^gının detaylarını sunmakta ve tek dizinli uygulamalara göre emtia mikro işlemciler ve Jerasure 2.0 yazılım kütüphanesini kullanarak önemli ölçüde performans artışının olabileceğini göstermektedir.WOS:000391250900420Conference Proceedings Citation Index- ScienceProceedings PaperMayıs2016YÖK - 2015-1

Compress-store on blockchain: a decentralized data processing and immutable storage for multimedia streaming

Decentralization for data storage is a challenging problem for blockchain-based solutions as the blocksize plays a key role for scalability. In addition, specific requirements of multimedia data call for various changes in the blockchain technology internals. Considering one of the most popular applications of secure multimedia streaming, i.e., video surveillance, it is not clear how to judiciously encode incentivization, immutability, and compression into a viable ecosystem. In this study, we provide a genuine scheme that achieves this encoding for a video surveillance application. The proposed scheme provides a novel integration of data compression, immutable off-chain data storage using a new consensus protocol namely, Proof-of-WorkStore (PoWS) in order to enable fully useful work to be performed by the miner nodes of the network. The proposed idea is the first step towards achieving greener application of a blockchain-based environment to the video storage business that utilizes system resources efficiently.WOS:000773171200001Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ2 - Q4Article; Early AccessUluslararası işbirliği ile yapılan - EVETNisan2022YÖK - 2021-22Mar

Base Station-Assisted Cooperative Network Coding for Cellular Systems with Link Constraints

We consider a novel distributed data storage/caching scenario in a cellular network, where multiple nodes may fail/depart simultaneously To meet reliability, we allow cooperative regeneration of lost nodes with the help of base stations allocated in a set of hierarchical layers1. Due to this layered structure, a symbol download from each base station has a different cost, while the link capacities between the nodes of the cellular system and the base stations are also constrained. Under such a setting, we formulate the fundamental trade-off with closed form expressions between repair bandwidth cost and the storage space per node. Particularly, the minimum storage as well as bandwidth cost points are formulated. Finally, we provide an explicit optimal code construction for the minimum storage regeneration point for a special set of system parameters.Scopus - Affiliation ID: 60105072Hazira

Service-aware multi-resource allocation in software-defined next generation cellular networks

Şefik Şuayb Arslan (MEF Author)Network slicing is one of the major solutions needed to meet the requirements of next generation cellular networks, under one common network infrastructure, in supporting multiple vertical services provided by mobile network operators. Network slicing makes one shared physical network infrastructure appear as multiple logically isolated virtual networks dedicated to different service types where each Network Slice (NS) benefits from on-demand allocated resources. Typically, the available resources distributed among NSs are correlated and one needs to allocate them judiciously in order to guarantee the service, MNO, and overall system qualities. In this paper, we consider a joint resource allocation strategy that weights the significance of the resources per a given NS by leveraging the correlation structure of different quality-of-service (QoS) requirements of the services. After defining the joint resource allocation problem including the correlation structure, we propose three novel scheduling mechanisms that allocate available network resources to the generated NSs based on different type of services with different QoS requirements. Performance of the proposed schedulers are then investigated through Monte-Carlo simulations and compared with each other as well as against a traditional max-min fairness algorithm benchmark. The results reveal that our schedulers, which have different complexities, outperform the benchmark traditional method in terms of service-based and overall satisfaction ratios, while achieving different fairness index levels.WOS:000430793600019Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ1 - Q2ArticleUluslararası işbirliği ile yapılmayan - HAYIRMart2018YÖK - 2017-1

LDPC kodlarında artık veri kullanımı

In distributed storage systems/coded caching systems, padding operations should be performed when the encoded data cannot be divided by the number of storage nodes evenly. Thus, extra zero values are stored in one of the nodes to balance each node’s storage content. In this study, distribution of data to storage nodes with no padding was investigated for distributed caching context in which a base station and devices both store the coded data. In other words, no redundancy (no-padding) is included into the encoded data. This approach is named as residual data distribution. LDPC codes are selected as the erasure code due to their low complexity encode/decode operations. Moreover, performance comparisons were conducted between using traditional data distribution approach (with padding) and using residual data (use of no-padding) (standard) in terms of repair time. In our work, the effect of no-padding data usage on the repair time and the ratios of storage savings have been also demonstrated.Dağıtık sistemlerde ve dağıtık ön-bellekleme sistemlerinde, kodlanmış veri boyutu depolama düğümü sayısına tam olarak bölünemediğinde genel olarak fazladan veri depolama işlemi gerçekleştirilmektedir. Bu çalışmada, baz istasyonunun ve düğümlerin kodlanmış veriyi depoladığı bir ön-bellekleme sistemi için, fazladan veri eklenmeden kodlanmış sembollerin depolama düğümlerine dağıtılması konusu incelenmiştir. Silinti kodları olarak zaman açısından yüksek kodlama verimliliğine sahip LDPC kodları kullanılmış olup düğüm tamir zamanı açısından fazladan verinin kaydedildiği kodlanmış veri paylaştırımı yaklaşımı ile fazladan verinin kullanılmadığı (artık veri paylaştırımı) kodlanmış veri paylaştırımı yaklaşımlarının performansı karşılaştırılmıştır. Bu kapsamda düğüm tamiri zamanı ile toplamda depolanması gereken verinin miktarı ile ilgili sonuçlar elde edilmiştir.Scopus - Affiliation ID: 6010507

Advancements in distributed ledger technology for Internet of Things

Internet of Things (IoT) is paving the way for different kinds of devices to be connected and properly communicated at a mass scale. However, conventional mechanisms used to sustain security and privacy cannot be directly applied to IoT whose topology is increasingly becoming decentralized. Distributed Ledger Technologies (DLT) on the other hand comprise varying forms of decentralized data structures that provide immutability through cryptographically linking blocks of data. To be able to build reliable, autonomous and trusted IoT platforms, DLT has the potential to provide security, privacy and decentralized operation while adhering to the limitations of IoT devices. The marriage of IoT and DLT technology is not very recent. In fact many projects have been focusing on this interesting combination to address the challenges of smart cities, smart grids, internet of everything and other decentralized applications, most based on blockchain structures. In this special issue, the focus is on the new and broader technical problems associated with the DLT-based security and backend platform solutions for IoT devices and applications.WOS:000695693900012Scopus - Affiliation ID: 60105072Science Citation Index ExpandedArticleUluslararası işbirliği ile yapılan - EVETMart2020YÖK - 2019-2

Network attached device for accessing removable storage media

Embodiments disclosed herein provide systems, methods, and computer readable media to access data on removable storage media via a network attached access device. In a particular embodiment, a method provides receiving one or more user provided, in the removable storage media access device, receiving data over a packet communication network for storage on a removable storage medium. After receiving the data, the method provides preparing the data for storage on the removable storage medium. After preparing the data, the method provides writing the data to the removable storage medium

Array BP-XOR codes for hierarchically distributed matrix multiplication

A novel fault-tolerant computation technique based on array Belief Propagation (BP)-decodable XOR (BP-XOR) codes is proposed for distributed matrix-matrix multiplication. The proposed scheme is shown to be configurable and suited for modern hierarchical compute architectures such as Graphical Processing Units (GPUs) equipped with multiple nodes, whereby each has many small independent processing units with increased core-to-core communications. The proposed scheme is shown to outperform a few of the well–known earlier strategies in terms of total end-to-end execution time while in presence of slow nodes, called stragglers. This performance advantage is due to the careful design of array codes which distributes the encoding operation over the cluster (slave) nodes at the expense of increased master-slave communication. An interesting trade-off between end-to-end latency and total communication cost is precisely described. In addition, to be able to address an identified problem of scaling stragglers, an asymptotic version of array BP-XOR codes based on projection geometry is proposed at the expense of some computation overhead. A thorough latency analysis is conducted for all schemes to demonstrate that the proposed scheme achieves order-optimal computation in both the sublinear as well as the linear regimes in the size of the computed product from an end-to-end delay perspective.WOS:000757850700039Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ2-Q3ArticleUluslararası işbirliği ile yapılmayan - HAYIRMart2022YÖK - 2021-22Aralı