Doctor of Philosophy, The Ohio State University, 2020, Computer Science and Engineering

Replication has been a cornerstone of reliable distributed storage systems for years. Replicating data at multiple locations in the system maintains sufficient redundancy to tolerate individual failures. However, the exploding volume and speed of data growth let researchers and engineers think about using storage-efficient fault tolerance mechanisms to replace replication in designing or re-designing reliable distributed storage systems. One promising alternative of replication is Erasure Coding (EC), which trades off extra computation for high reliability and availability at a prominently low storage overhead. Therefore, many existing distributed storage systems (e.g., HDFS 3.x, Ceph, QFS, Google Colossus, Facebook f4, and Baidu Atlas) have started to adopt EC to achieve storage-efficient fault tolerance. However, as EC introduces extra calculations into systems, there are several crucial challenges to think through for exploiting EC. Such as how to leverage heterogeneous EC-capable hardware (e.g., CPUs, General-Purpose Graphics Processing Units (GPGPUs), Field-Programmable Gate Arrays (FPGAs), and Smart Network Interface Cards (SmartNICs)) to accelerate EC computation and bring emergent devices and technologies into the pictures for designing high-performance erasure-coded distributed storage systems. In this dissertation, we propose Mint-EC, a high-performance EC framework to address the aforementioned research challenges. Mint-EC includes three major pillars: 1) a multi-rail EC library that enables upper-layer applications to leverage heterogeneous EC-capable hardware devices to perform EC operations simultaneously and introduces unified APIs to facilitate overlapping opportunities between computation and communication, 2) a set of coherent in-network EC primitives that can be easily integrated into existing state-of-the-art EC schemes and utilized in designing advanced EC schemes to fully leverage the advantages of the coherent in-network EC capabilities on (open full item for complete abstract)

Committee: Xiaoyi Lu (Advisor); Xiaodong Zhang (Committee Member); Christopher Stewart (Committee Member); Yang Wang (Committee Member) Subjects: Computer Engineering; Computer Science

Master of Arts, The Ohio State University, 2011, Near Eastern Languages and Cultures

Western scholars and Muslim exegetes alike are of one voice in conceptualizing the Qur'anic verb ‘aqala as "understand." Noting an opportunity to pry at a rarely-questioned spot in the consensus of Qur'anic studies, this thesis attempts – following the methodologies of Richter (1971) and Isutzu (1995, 2002) and within the framework given by Noldeke and Schwally (1909) – to expose new semantic depths of the root ‘-q-l (occurring exclusively as the verb ‘aqala) as it appears in the Qur'an. Using a diachronic literary, syntactic, semantic, and lexical approach, the depth of the field(s) occupied by ‘-q-l will be explored, providing insights potentially valuable to translators and students of the Qur'an.

Committee: Georges Tamer PhD (Advisor); Snjezana Buzov PhD (Committee Member); Bruce Fudge PhD (Committee Member) Subjects: Islamic Studies; Middle Eastern Studies; Religion; Sociolinguistics

Doctor of Philosophy, The Ohio State University, 2010, Electrical and Computer Engineering

Emerging broadband applications with market pressures for miniaturized communication devices have encouraged the use of electrically small antennas (ESA) and highly integrated RF circuitry for high volume low cost mobile devices. This research work focuses on developing a novel scheme to design wideband electrical small antennas that incorporates active and passive loading as well as passive matching networks. Several antennas designed using the proposed design technique and built and measured to assess their performance and to validate the design methodology. Previously, the theory of Characteristic Modes (CM) has been used mostly for antennas analysis. However; in this chapter a design procedure is proposed for designing wide band (both the input impedance bandwidth and the far field pattern bandwidth) electrically small to mid size antennas using the CM in conjunction with the theory of matching networks developed by Carlin. In order to increase the antenna gain, the antenna input impedance mismatch loss needs to be minimized by carefully exciting the antenna either at one port or at multiple ports and/or load the antenna at different ports along the antenna body such that the Q factor in the desired frequency range is suitable for wideband matching network design. The excitation (feeding structure), the loading of the antenna and/or even small modifications to the antenna structure can be modeled and understood by studying the eigenvalues and their corresponding eigencurrents obtained from the CM of the antenna structure. A brief discussion of the theory of Characteristic Modes (CM) will be presented and reviewed before the proposed design scheme is introduced. The design method will be used to demonstrate CM applications to widen the frequency bandwidth of the input impedance of an electrically small Vee shape Antenna and to obtain vertically polarized Omni-directional patterns for such antenna over a wide bandwidth. A loading technique based on the CM to eith (open full item for complete abstract)

Committee: Roberto G. Rojas PhD (Advisor); Garbacz Robert PhD (Committee Member); Teixeira Fernando PhD (Committee Member) Subjects: Electrical Engineering; Engineering; Experiments

Doctor of Philosophy, The Ohio State University, 2003, Computer and Information Science

Cluster computing systems are becoming increasingly popular computing environments for day-to-day computational needs because they are cost-effective and affordable. While clusters are considerably less expensive than massively parallel processors (MPPs), MPP communication performance is typically much better than cluster communication performance. Some modern network interface controllers (NICs) have programmable processors which can be used to offload communications processing from the host processor. Process skew is inherent in cluster communication systems. Some processes may be delayed, relative to other processes, due to various unavoidable causes. Many collective communication operations are implemented in a manner in which all participating processes need to perform the operation in order for the operation to proceed. This means that if one process is delayed, it may cause other processes to be delayed when performing a collective operation. This dissertation investigates the use of programmable NICs to improve cluster performance. We approach this problem by focusing on improving the performance, scalability, and tolerance to process skew of synchronization operations and collective communication operations through the use of NIC-based operations and NIC-based primitives. NIC-based operations and primitives improve the performance of cluster systems. Latency is improved in some operations by performing the operation directly at the NIC and avoiding sending messages over the slow I/O bus. Host processor utilization is improved because host processor involvement in the operation is reduced. This also allows computation to be overlapped with the operation. NIC-based operations are also less sensitive to process skew. To demonstrate the effect of NIC based operations, we have designed and implemented NIC-supported broadcast/multicast, barrier synchronization, reduction and atomic remote memory operations, as well as a application-bypass broadcast on Myrinet/GM (open full item for complete abstract)

Committee: Dhabaleswar Panda (Advisor) Subjects: Computer Science