Browsing by Subject "Storage"
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Item A New I/O Scheduler for Solid State Devices(2010-10-12) Dunn, Marcus P.Since the emergence of solid state devices onto the storage scene, improvements in capacity and price have brought them to the point where they are becoming a viable alternative to traditional magnetic storage for some applications. Current file system and device level I/O scheduler design is optimized for rotational magnetic hard disk drives. Since solid state devices have drastically different properties and structure, we may need to rethink the design of some aspects of the file system and scheduler levels of the I/O subsystem. In this thesis, we consider the current approach to I/O scheduling and show that the current scheduler design may not be ideally suited to solid state devices. We also present a framework for extracting some device parameters of solid state drives. Using the information from the parameter extraction, we present a new I/O scheduler design which utilizes the structure of solid state devices to efficiently schedule writes. The new scheduler, implemented on a 2.6 Linux kernel, shows up to 25% improvement for common workloads.Item An Electrolytic Method to Form Zirconium Hydride Phases in Zirconium Alloys with Morphologies Similar to Hydrides Formed in Used Nuclear Fuel(2012-10-19) Kuhr, Samuel HoustonAn electrolytic cell was designed, built, and tested with several proof-of-concept experiments in which Zircaloy material was charged with hydrogen in order to generate zirconium hydride formations. The Electrolytic Charging with Hydrogen and a Thermal Gradient (ECH-TG) system has the ability to generate static 20?C to 120?C temperatures for a H2SO4 and H2O bath for isothermal experiment conditions. This system was designed to accommodate a molten salt bath in future experiments to achieve higher isothermal temperatures. Additionally, the design accommodates a cartridge heater, which when placed on the inside of the sample tube, can be set at temperatures up to 350 ?C and create a thermal gradient across the sample. Finally, a custom LABVIEW VI, L2.vi, was developed to control components and record data during experimentation. This program, along with web cameras and the commercial StirPC software package, enables remote operation for extended periods of time with only minor maintenance during an experiment. While proving the concept for this design, 19 experiments where performed, which form the basis for a future parametric study. Initial results indicate formations of zirconium hydrides which formed rim structures between 8.690 +/- 0.982 ?m and 12.365 +/- 0.635 ?m thick. These electrolytically produced rims were compared with hydrides formed under a previous vapor diffusion experiment via Scanning Electron Microscope (SEM) imaging and Energy dispersive X-ray Spectroscopy (EDS) analysis. While the existing vapor diffusion method formed gradients of zirconium hydride, it failed to produce the gradient in the correct direction and also failed to create a hydride rim. The successful use of the ECH-TG system to create said rim, and some of the methods used to direct that rim to the OD of the tube can be used for future work with the vapor diffusion method in order to create zirconium hydrides of the correct geometry. The procedures and apparatus created for this project represent a reliable method for creating zirconium hydride rim structures.Item A dynamic model-based estimate of the potential value of a vanadium redox flow battery for energy arbitrage and frequency regulation in Texas(2012-08) Fares, Robert Leo; Webber, Michael E., 1971-; Meyers, Jeremy P.Large-scale electrochemical energy storage is a technology that is uniquely suited to integrate intermittent renewable energy sources with the electric grid on a large scale. Grid-based energy storage also has the potential to reduce costs associated with periods of peak electric demand. For these reasons, this work describes the potential applications for grid-based energy storage, and then reviews large-scale energy storage technology innovations since the development of the lead-acid battery. The potential value of grid-based battery energy storage is discussed in the context of restructured electricity markets; then, a dynamic model-based economic optimization routine is developed to gauge the potential value of a vanadium redox flow battery (VRFB) operating for wholesale energy arbitrage and frequency regulation in Texas. Based on this analysis, the relative value of a VRFB in various regions of Texas for energy arbitrage and frequency regulation is examined. It is shown that frequency regulation is an appealing application for a grid-based VRFB, with a VRFB utilized for frequency regulation service in Texas potentially worth approximately $1500/kW. Finally, the effect of a VRFB’s characteristics on its value for frequency regulation and energy arbitrage are compared, and the operational insight developed in this work is used to glean how policies to integrate a large-scale energy storage with the electricity market might be crafted.Item Late to terminal classic household strategies : an exploration of the art of feasting, storage, and gifting at La Milpa, Belize(2014-12) Riddick, Deanna Marie; Valdez, Fred, Jr., 1953-This dissertation explores the social and political strategies performed by an intermediate elite household, Sak Ch'en, in an effort to maintain their social status and power in the evolving landscape of La Milpa during the Late to Terminal Classic Transition (A.D. 800-850/900). Explicitly, this research investigates how Sak Ch'en preserved the continuity of social order by exercising their funds of power and by feasting, gifting, and storing socially charged goods. Excavations were conducted at one residential complex during the 2009-2012 field seasons at the site of La Milpa, Belize, to delineate the political, social, and economic dimensions of intermediate elite household life during large-scale structural changes of the polity. Analyses of recovered ceramic assemblages and additional artifacts demonstrate the presence of feasting, the storage of socially valuable goods, and the production of cloth items during the Late to Terminal Classic period. Feasting in Maya society was enacted as a social, political, and economic strategy, which enabled the ruling elite to attract political support and create exclusive alliances. It is my deduction that at Sak Ch'en, feasting operated as a forum to display household rank, validate status, and maintain power through food acquisition, production, consumption, and distribution. By hosting a feast, Sak Ch'en inhabitants solidified existing political and socioeconomic relationships and encouraged the development of new household associations. Analyses of spindle whorls at Sak Ch'en revealed the production of cloth goods for local consumption and possibly gift exchange. Gift-giving may have been employed at Sak Ch'en as a strategy that binded individuals or groups into reciprocal debt relationships. Further, the gifting of food during this unstable period publicly displayed access to, or possession of, surplus at Sak Ch'en, which strongly reiterated asymmetrical economic power relations between households. Lastly, the storage of goods reassured the replication of activities and rituals tied to ideological concepts of social order. These strategies were implemented at Sak Ch'en as reiterative mechanisms operating to guarantee the reproduction of household power and status.Item Quantifying thermally driven fracture geometry during CO₂ storage(2014-12) Taylor, Jacob Matthew; Bryant, Steven L.The desired lifetime for CO₂ injection for sequestration is several decades at a high injection rate (up to 10 bbl/min or 2,400 tons/day per injector). Government regulations and geomechanical design constraints may impose a limit on the injection rate such that, for example, the bottomhole pressure remains less than 90% of the hydraulic fracture pressure. Despite injecting below the critical fracture pressure, fractures can nevertheless initiate and propagate due to a thermoelastic stress reduction caused by cool CO₂ encountering hot reservoir rock. Here we develop a numerical model to calculate whether mechanical and thermal equilibrium between the injected CO₂ and the reservoir evolves, such that fracture growth ceases. When such a condition exists, the model predicts the corresponding fracture geometry and time to reach that state. The critical pressure for fracture propagation depends on the thermoelastic stress, a function of rock properties and the temperature difference between the injected fluid and the reservoir (ΔT). Fractures will propagate as long as the thermoelastic stress and the fluid pressure at the fracture tip exceed a threshold; we calculate the extent of a fracture such that the tip pressure falls below the thermoelastically modified fracture propagation pressure. Fracture growth is strongly dependent upon the formation permeability, the level of injection pressure above fracture propagation pressure, and ΔT.Item Resource-constrained, scalable learning(2015-08) Mitliagkas, Ioannis; Vishwanath, Sriram; Caramanis, Constantine; Dimakis, Alex; Sanghavi, Sujay; Ravikumar, PradeepOur unprecedented capacity for data generation and acquisition often reaches the limits of our data storage capabilities. Situations when data are generated faster or at a greater volume than can be stored demand a streaming approach. Memory is an even more valuable resource. Algorithms that use more memory than necessary can pose bottlenecks when processing high-dimensional data and the need for memory-efficient algorithms is especially stressed in the streaming setting. Finally, network along with storage, emerge as the critical bottlenecks in the context of distributed computation. These computational constraints spell out a demand for efficient tools that guarantee a solution in the face of limited resources, even when the data is very noisy or highly incomplete. For the first part of this dissertation, we present our work on streaming, memory-limited Principal Component Analysis (PCA). Therein, we give the first convergence guarantees for an algorithm that solves PCA in the single-pass streaming setting. Then, we discuss the distinct challenges that arise when the received samples are overwhelmingly incomplete and present an algorithm and analysis that deals with this issue. Finally, we give a set of extensive experiment results that showcase the practical merits of our algorithm over the state of the art. The need for heavy network communication arises as the bottleneck when dealing with cluster computation. In that paradigm, a set of worker nodes are connected over the network to produce a cluster with improved computational and storage capacities. This comes with an increased need for communication across the network. In the last part of this work, we consider the problem of PageRank on graph engines. Therein, we make changes to GraphLab, a state-of-the-art platform for distributed graph computation, in a way that leads to a 7x-10x speedup for certain PageRank approximation tasks. Accompanying analysis supports the behaviour we see in our experiments.Item Separating data from metadata for robustness and scalability(2014-12) Wang, Yang, Ph. D.; Alvisi, Lorenzo; Dahlin, MichaelWhen building storage systems that aim to simultaneously provide robustness, scalability, and efficiency, one faces a fundamental tension, as higher robustness typically incurs higher costs and thus hurts both efficiency and scalability. My research shows that an approach to storage system design based on a simple principle—separating data from metadata—can yield systems that address elegantly and effectively that tension in a variety of settings. One observation motivates our approach: much of the cost paid by many strong protection techniques is incurred to detect errors. This observation suggests an opportunity: if we can build a low-cost oracle to detect errors and identify correct data, it may be possible to reduce the cost of protection without weakening its guarantees. This dissertation shows that metadata, if carefully designed, can serve as such an oracle and help a storage system protect its data with minimal cost. This dissertation shows how to effectively apply this idea in three very different systems: Gnothi—a storage replication protocol that combines the high availability of asynchronous replication and the low cost of synchronous replication for a small-scale block storage; Salus—a large-scale block storage with unprecedented guarantees in terms of consistency, availability, and durability in the face of a wide range of server failures; and Exalt—a tool to emulate a large storage system with 100 times fewer machines.Item Storage Systems for Non-volatile Memory Devices(2011-10-21) Wu, XiaojianThis dissertation presents novel approaches to the use of non-volatile memory devices in building storage systems. There are many types of non-volatile memory devices, and they usually have better performance than regular magnetic hard disks in terms of throughput and latency. This dissertation focused on two of them, NAND flash memory and Phase Change Memory (PCM). This work consisted of two parts. The first part was to design a high-performance hybrid storage system employing Solid State Drives that are build out of NAND flash memory and Hard Disk Drives. In this hybrid system, we proposed two different policies to improve its performance. One is to exploit the fact that the performances of Solid State Drive and Hard Disk Drive are asymmetric and the other is to exploit concurrency on multiple devices. We implemented prototypes in Linux and evaluate both policies in multiple workloads and multiple configurations. The results showed that the proposed approaches improve the performance significantly, and adapt to different configurations of the system under different workloads. The second part was to implement a file system on a special class of memory devices, Storage Class Memory (SCM), which is both byte addressable and also nonvolatile, e.g. PCM. We claimed that both the existing regular file systems and the memory based file systems are not suitable for SCM, and proposed a new file system, called SCMFS, which is implemented on the virtual address space. In SCMFS, we utilized the existing memory management module in the operating system to do the block management. Our design keeps address space within a file contiguous to reduce the block management software. The simplicity of SCMFS not only makes it easy to implement, but also improves the performance. We implemented a prototype of SCMFS in Linux and evaluated its performance through multiple benchmarks.Item Storageflow: An SDN Approach to Storage Networks(2014-08-04) Bose, PradiptaNetwork Attached Storage (NAS) systems have become popular due to their efficiency, ease of use, and ability to protect and restore data. Many NAS implementations provide efficient service and utilize sophisticated techniques such as coding and striping of data to better utilize the available space, provide fast recovery from disk failures and avoid loss of data. Unfortunately, the current architectures are complex and inflexible which necessitates the need to introduce greater flexibility and support for experimentation. Additionally, there is a significant potential to improve the performance of the system by leveraging regenerative coding techniques and by allowing the intermediate network nodes to perform encoding operations. OpenFlow (OF) is a rich SDN protocol that has gained significant popularity in recent years. OpenFlow defines a standard communications interface between the control and forwarding layers of an SDN architecture, as well as the forwarding architecture of a switch. While OpenFlow currently supports only a limited number set of protocols, it has attracted significant attention from both industry as well as research community and has significant potential to be widely adopted by the industry. The key idea of this thesis is to utilize multifunctional SDN-enabled switches that can perform both traditional forwarding operations as well as new encoding operation on the packets. For this purpose, we propose to extend the OpenFlow datapath by enabling the switch to perform encoding operations on select flows upon the request from the controller. Our approach utilizes commodity hardware, which makes it cost-efficient and attractive. In contrast to the traditional approaches which rely on dedicated servers to perform coding and striping operations, our approach has better performance and flexibility, and can be easily customized to serve the requirements of a particular storage scheme. In addition, our approach makes it easier to experiment with new applications, including the use of different encoding schemes by enabling fast prototyping and testing. Since none of the existing SDN protocols (including OpenFlow) provide support for basic storage functions such as striping and coding, we propose several extensions of the OpenFlow protocol to support such functionality as well as encoding operations. The extensions we develop are part of a systematic approach to design an SDN-enabled NAS system. We identify some common design trade-offs and evaluate their impacts on performance and reliability. Furthermore, the thesis presents a forwarding data path extension that uses custom data structures and groups at the switch. This design also effectively reduces required bandwidth and enables traffic engineering and load balancing at network links.Item Sugar Stability of Sweet Sorghum Exposed to Climate Controlled and Ambient Storage Conditions(2014-08-22) Herb, Dustin WalkerHistorically, crop based ethanol has predominantly been achieved in the United States through starch-based and sugar-based conversions. With corn being one of the leading food and feed crops in the United States, and sugarcane?s inability to adapt to U.S. production regions, Sorghum (Sorghum bicolor L. Moench) has been identified as a potential alternative biofuel feedstock. The objective of this study was to evaluate the stability of non-structural carbohydrates (sugar) present in sweet sorghum juice, by tracking the sugar degradation of ?Dale? and ?M81E? while exposed to extended periods of climate controlled and ambient conditions after peak sugar accumulation. The data from both genotypes indicated that sugar yields can be sustained for weeks without significant losses. The plants left in the field for the ambient treatment continued sugar accumulation until photosynthesis and transpiration halted, causing immediate loss in sugar. Samples under the controlled treatment retained sugar yields for 3-4 weeks with minimal losses in yield, followed by a steady reduction for the remainder of the evaluations. However, the overall sugar loss after 70 days was comparable between treatments, which leads to the conclusion that sweet sorghum has the potential to be stored up to four weeks before significant yield loss occurs, regardless of storage methods. Combining staggering sweet sorghum plantings with short-term storage to sugarcane productions makes sorghum a suitable alternative or complementary feedstock to current sugar-based ethanol refineries.Item The effects of cooking, storage, and ionizing irradiation on carotenoids, antioxidant activity, and phenolics in potato (Solanum tuberosum L.)(Texas A&M University, 2005-11-01) Blessington, TyannPast research conducted by our lab demonstrated that potatoes contain significant levels of phytochemicals important to human health. However, since potatoes are not consumed raw, it is important to determine the effects of processing on these levels. Therefore, the changes in carotenoid content, antioxidant activity, and phenolic content were investigated using combinations of cultivars, cooking methods, storage treatments, and low-dose ionizing irradiation. Carotenoid content was measured via absorbance at 445 nm, 450 nm, and HPLC identification. Antioxidant activity was measured initially and at stabilization via the DPPH method and phenolic content was measured via the Folin method and HPLC identification. Microwaved, baked, fried, and raw potato samples contained more carotenoids than boiled samples. The samples microwaved, baked, and fried contained higher antioxidant activity and phenolics than the boiled or raw samples. However, the compound quercetin dihydrate appeared to decrease with cooking. Carotenoids, antioxidant activity, and phenolics appeared to decrease with storage; however, high storage temperatures and long storage times were believed to cause a dehydration and concentration of compounds, which caused levels to be equal to or greater than before storage. However, this decreasing trend was not linear and there were multiple significant interactions. The compound chlorogenic acid appeared to be quite sensitive to high temperature storage. Irradiation dose appeared to have only a minor, if any, effect on carotenoid levels. The interaction between storage time and irradiation dose was very influential on antioxidant activity. In early stages of storage, higher doses of irradiation had greater antioxidant activity, while, with continued storage, low doses had higher antioxidant activity. Exposure to irradiation appeared to cause an increase in phenolic content, determined by the Folin method. There may be a stimulation, induction, or release of some compounds due to processing; however, its magnitude is not believed to be as great as genetic control. The effects of processing can not be denied and should continue to be investigated. Future studies investigating the health properties of fruits and vegetables, particularly potatoes should include processing effects.