A Taxonomy of Data Grids for Distributed Data Sharing, Management and Processing

Data Grids have been adopted as the platform for scientific communities that need to share, access, transport, process and manage large data collections distributed worldwide. They combine high-end computing technologies with high-performance networking and wide-area storage management techniques. In this paper, we discuss the key concepts behind Data Grids and compare them with other data sharing and distribution paradigms such as content delivery networks, peer-to-peer networks and distributed databases. We then provide comprehensive taxonomies that cover various aspects of architecture, data transportation, data replication and resource allocation and scheduling. Finally, we map the proposed taxonomy to various Data Grid systems not only to validate the taxonomy but also to identify areas for future exploration. Through this taxonomy, we aim to categorise existing systems to better understand their goals and their methodology. This would help evaluate their applicability for solving similar problems. This taxonomy also provides a "gap analysis" of this area through which researchers can potentially identify new issues for investigation. Finally, we hope that the proposed taxonomy and mapping also helps to provide an easy way for new practitioners to understand this complex area of research.Comment: 46 pages, 16 figures, Technical Repor

Leveraging Emerging Hardware to Improve the Performance of Data Analytics Frameworks

Department of Computer Science and EngineeringThe data analytics frameworks have evolved along with the growing amount of data. There have been numerous efforts to improve the performance of the data analytics frameworks in- cluding MapReduce frameworks and NoSQL and NewSQL databases. These frameworks have various target workloads and their own characteristicshowever, there is common ground as a data analytics framework. Emerging hardware such as graphics processing units and persistent memory is expected to open up new opportunities for such commonality. The goal of this dis- sertation is to leverage emerging hardware to improve the performance of the data analytics frameworks. First, we design and implement EclipseMR, a novel MapReduce framework that efficiently leverages an extensive amount of memory space distributed among the machines in a cluster. EclipseMR consists of a decentralized DHT-based file system layer and an in-memory cache layer. The in-memory cache layer is designed to store both local and remote data while balancing the load between the servers with proposed Locality-Aware Fair (LAF) job scheduler. The design of EclipseMR is easily extensible with emerging hardwareit can adopt persistent memory as a primary storage layer or cache layer, or it can adopt GPU to improve the performance of map and reduce functions. Our evaluation shows that EclipseMR outperforms Hadoop and Spark for various applications. Second, we propose B 3 -tree and Cache-Conscious Extendible Hashing (CCEH) for the persis- tent memory. The fundamental challenge to design a data structure for the persistent memory is to guarantee consistent transition with 8-bytes of fine-grained atomic write with minimum cost. B 3 -tree is a fully persistent hybrid indexing structure of binary tree and B+-tree that benefits from the strength of both in-memory index and block-based index, and CCEH is a variant of extendible hashing that introduces an intermediate layer between directory and buckets to fully benefit from a cache-sized bucket while minimizing the size of the directory. Both of the data structures show better performance than the corresponding state-of-the-art techniques. Third, we develop a data parallel tree traversal algorithm, Parallel Scan and Backtrack (PSB), for k-nearest neighbor search problem on the GPU. Several studies have been proposed to improve the performance of the query by leveraging GPU as an acceleratorhowever, most of the works focus on the brute-force algorithms. In this work, we overcome the challenges of traversing multi-dimensional hierarchical indexing structure on the GPU such as tiny shared memory and runtime stack, irregular memory access pattern, and warp divergence problem. Our evaluation shows that our data parallel PSB algorithm outperforms both the brute-force algorithm and the traditional branch and bound algorithm.clos

Energy-Aware Data Management on NUMA Architectures

The ever-increasing need for more computing and data processing power demands for a continuous and rapid growth of power-hungry data center capacities all over the world. As a first study in 2008 revealed, energy consumption of such data centers is becoming a critical problem, since their power consumption is about to double every 5 years. However, a recently (2016) released follow-up study points out that this threatening trend was dramatically throttled within the past years, due to the increased energy efficiency actions taken by data center operators. Furthermore, the authors of the study emphasize that making and keeping data centers energy-efficient is a continuous task, because more and more computing power is demanded from the same or an even lower energy budget, and that this threatening energy consumption trend will resume as soon as energy efficiency research efforts and its market adoption are reduced. An important class of applications running in data centers are data management systems, which are a fundamental component of nearly every application stack. While those systems were traditionally designed as disk-based databases that are optimized for keeping disk accesses as low a possible, modern state-of-the-art database systems are main memory-centric and store the entire data pool in the main memory, which replaces the disk as main bottleneck. To scale up such in-memory database systems, non-uniform memory access (NUMA) hardware architectures are employed that face a decreased bandwidth and an increased latency when accessing remote memory compared to the local memory. In this thesis, we investigate energy awareness aspects of large scale-up NUMA systems in the context of in-memory data management systems. To do so, we pick up the idea of a fine-grained data-oriented architecture and improve the concept in a way that it keeps pace with increased absolute performance numbers of a pure in-memory DBMS and scales up on NUMA systems in the large scale. To achieve this goal, we design and build ERIS, the first scale-up in-memory data management system that is designed from scratch to implement a data-oriented architecture. With the help of the ERIS platform, we explore our novel core concept for energy awareness, which is Energy Awareness by Adaptivity. The concept describes that software and especially database systems have to quickly respond to environmental changes (i.e., workload changes) by adapting themselves to enter a state of low energy consumption. We present the hierarchically organized Energy-Control Loop (ECL), which is a reactive control loop and provides two concrete implementations of our Energy Awareness by Adaptivity concept, namely the hardware-centric Resource Adaptivity and the software-centric Storage Adaptivity. Finally, we will give an exhaustive evaluation regarding the scalability of ERIS as well as our adaptivity facilities

Yellow Tree: A Distributed Main-memory Spatial Index Structure for Moving Objects

Mobile devices equipped with wireless technologies to communicate and positioning systems to locate objects of interest are common place today, providing the impetus to develop location-aware applications. At the heart of location-aware applications are moving objects or objects that continuously change location over time, such as cars in transportation networks or pedestrians or postal packages. Location-aware applications tend to support the tracking of very large numbers of such moving objects as well as many users that are interested in finding out about the locations of other moving objects. Such location-aware applications rely on support from database management systems to model, store, and query moving object data. The management of moving object data exposes the limitations of traditional (spatial) database management systems as well as their index structures designed to keep track of objects\u27 locations. Spatial index structures that have been designed for geographic objects in the past primarily assume data are foremost of static nature (e.g., land parcels, road networks, or airport locations), thus requiring a limited amount of index structure updates and reorganization over a period of time. While handling moving objects however, there is an incumbent need for continuous reorganization of spatial index structures to remain up to date with constantly and rapidly changing object locations. This research addresses some of the key issues surrounding the efficient database management of moving objects whose location update rate to the database system varies from 1 to 30 minutes. Furthermore, we address the design of a highly scaleable and efficient spatial index structure to support location tracking and querying of large amounts of moving objects. We explore the possible architectural and the data structure level changes that are required to handle large numbers of moving objects. We focus specifically on the index structures that are needed to process spatial range queries and object-based queries on constantly changing moving object data. We argue for the case of main memory spatial index structures that dynamically adapt to continuously changing moving object data and concurrently answer spatial range queries efficiently. A proof-of concept implementation called the yellow tree, which is a distributed main-memory index structure, and a simulated environment to generate moving objects is demonstrated. Using experiments conducted on simulated moving object data, we conclude that a distributed main-memory based spatial index structure is required to handle dynamic location updates and efficiently answer spatial range queries on moving objects. Future work on enhancing the query processing performance of yellow tree is also discussed

Change Management Systems for Seamless Evolution in Data Centers

Revenue for data centers today is highly dependent on the satisfaction of their enterprise customers. These customers often require various features to migrate their businesses and operations to the cloud. Thus, clouds today introduce new features at a swift pace to onboard new customers and to meet the needs of existing ones. This pace of innovation continues to grow on super linearly, e.g., Amazon deployed 1400 new features in 2017. However, such a rapid pace of evolution adds complexities both for users and the cloud. Clouds struggle to keep up with the deployment speed, and users struggle to learn which features they need and how to use them. The pace of these evolutions has brought us to a tipping point: we can no longer use rules of thumb to deploy new features, and customers need help to identify which features they need. We have built two systems: Janus and Cherrypick, to address these problems. Janus helps data center operators roll out new changes to the data center network. It automatically adapts to the data center topology, routing, traffic, and failure settings. The system reduces the risk of new deployments for network operators as they can now pick deployment strategies which are less likely to impact users’ performance. Cherrypick finds near-optimal cloud configurations for big data analytics. It adapts allows users to search through the new machine types the clouds are constantly introducing and find ones with a near-optimal performance that meets their budget. Cherrypick can adapt to new big-data frameworks and applications as well as the new machine types the clouds are constantly introducing. As the pace of cloud innovations increases, it is critical to have tools that allow operators to deploy new changes as well as those that would enable users to adapt to achieve good performance at low cost. The tools and algorithms discussed in this thesis help accomplish these goals

Proceedings of the Second International Workshop on HyperTransport Research and Applications (WHTRA2011)

Proceedings of the Second International Workshop on HyperTransport Research and Applications (WHTRA2011) which was held Feb. 9th 2011 in Mannheim, Germany. The Second International Workshop for Research on HyperTransport is an international high quality forum for scientists, researches and developers working in the area of HyperTransport. This includes not only developments and research in HyperTransport itself, but also work which is based on or enabled by HyperTransport. HyperTransport (HT) is an interconnection technology which is typically used as system interconnect in modern computer systems, connecting the CPUs among each other and with the I/O bridges. Primarily designed as interconnect between high performance CPUs it provides an extremely low latency, high bandwidth and excellent scalability. The definition of the HTX connector allows the use of HT even for add-in cards. In opposition to other peripheral interconnect technologies like PCI-Express no protocol conversion or intermediate bridging is necessary. HT is a direct connection between device and CPU with minimal latency. Another advantage is the possibility of cache coherent devices. Because of these properties HT is of high interest for high performance I/O like networking and storage, but also for co-processing and acceleration based on ASIC or FPGA technologies. In particular acceleration sees a resurgence of interest today. One reason is the possibility to reduce power consumption by the use of accelerators. In the area of parallel computing the low latency communication allows for fine grain communication schemes and is perfectly suited for scalable systems. Summing up, HT technology offers key advantages and great performance to any research aspect related to or based on interconnects. For more information please consult the workshop website (http://whtra.uni-hd.de)

Design of efficient and elastic storage in the cloud

Ph.DDOCTOR OF PHILOSOPH

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: vehicular ad-hoc networks, security and caching, TCP in ad-hoc networks and emerging applications. It is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Creating a Concurrent In-Memory B-Tree Optimized for NUMA Systems

The size of main memory is becoming larger. With the number of Central Processing Unit (CPU) cores ever increasing in modern systems, with each of them being able to access memory, the organization of memory becomes more important. In multicore systems, there are two main architectures for memory organization with respect to the cores - Symmetric Multi-Processor (SMP) and Non-Uniform Memory Architecture (NUMA). Prior work has focused on the improvement of the performance of B-Trees in highly concurrent and distributed environments, as well as in memory, for shared-memory mul- tiprocessors. However, little focus has been given to the performance of main memory B-Trees for NUMA systems. This work focuses on improving the performance of B-Trees contained in main memory of NUMA systems by introducing modifications that consider its storage in the physically distributed main memory of the NUMA system. The work in this thesis makes the following contributions to the development of a distributed B-Tree, specifically in a NUMA environment, modified from a B-Tree originally designed for high concurrency: • It introduces replication of internal nodes of the tree and shows how this can improve its overall performance in a NUMA environment. • It introduces NUMA-aware locking procedures with the aim of managing contention and exploiting locality of lock requests with reference to previous client operation request locations. • It introduces changes in the granularity of locking, starting from the original locking of every node to the locking of certain levels of nodes, showing the tradeoff between the granularity of locking and the performance of the tree based on the workload. • It considers the combination of the different techniques, with the aim of finding the combination which performs well overall for varying read-heavy workloads and number of client threads

Efficient Passive Clustering and Gateways selection MANETs

Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets