Due to their tight isolation, low overhead, and efficient packaging of the execution environment, Docker containers have become a prominent solution for deploying modern applications. Consequently, a large amount of Docker images are created and this massive image dataset presents challenges to the registry and container storage infrastructure and so far has remained a largely unexplored area. Hence, there is a need of docker image characterization that can help optimize and improve the storage systems for containerized applications. Moreover, existing deduplication techniques significantly degrade the performance of registries, which will slow down the container startup time. Therefore, there is growing demand for high storage efficiency and high-performance registry storage systems. Last but not least, different storage systems can be integrated with containers as backend storage systems and provide persistent storage for containerized applications. So, it is important to analyze the performance of different backend storage systems and storage drivers and draw out the implications for container storage system design. These above observations and challenges motivate my dissertation. In this dissertation, we aim to improve the flexibility, performance, and efficiency of the storage systems for containerized applications. To this end, we focus on the following three important aspects: Docker images, Docker registry storage system, and Docker container storage drivers with their backend storage systems. Specifically, this dissertation adopts three steps: (1) analyzing the Docker image dataset; (2) deriving the design implications; (3) designing a new storage framework for Docker registries and propose different optimizations for container storage systems. In the first part of this dissertation (Chapter 3), we analyze over 167TB of uncompressed Docker Hub images, characterize them using multiple metrics and evaluate the potential of le level deduplication in Docker Hub. In the second part of this dissertation (Chapter 4), we conduct a comprehensive performance analysis of container storage systems based on the key insights from our image characterizations, and derive several design implications. In the third part of this dissertation (Chapter 5), we propose DupHunter, a new Docker registry architecture, which not only natively deduplicates layers for space savings but also reduces layer restore overhead. DupHunter supports several configurable deduplication modes, which provide different levels of storage efficiency, durability, and performance, to support a range of uses. In the fourth part of this dissertation (Chapter 6), we explore an innovative holistic approach, Chameleon, that employs data redundancy techniques such as replication and erasure-coding, coupled with endurance-aware write offloading, to mitigate wear level imbalance in distributed SSD-based storage systems. This high-performance fash cluster can be used for registries to speedup performance. / Doctor of Philosophy / The amount of Docker images stored in Docker registries is increasing rapidly and present challenges for the underlying storage infrastructures. Before we do any optimizations for the storage system, we should first analyze this big Docker image dataset. To this end, in this dissertation we perform the first large-scale characterization and redundancy analysis of the images and layers stored in the Docker Hub registry. Based on the findings, this dissertation presents a series of practical and efficient techniques, algorithms, optimizations to achieve high performance and flexibility, and space-efficient storage system for containerized applications. The experimental evaluation demonstrates the effectiveness of our optimizations and techniques to make storage systems flexible and space-efficacy.

In the last two-decades data center networks have evolved to become a key element in improving levels of productivity and competitiveness for different types of organizations. Traditionally data center networks have been constructed with 3 layers of switches, Edge, Aggregation, and Core. Although this Three-Tier architecture has worked well in the past, it poses a number of challenges for current and future data centers. Data centers today have evolved to support dynamic resources such as virtual machines and storage volumes from any physical location within the data center. This has led to highly volatile and unpredictable traffic patterns. Also The emergence of "Big Data" applications that exchange large volumes of information have created large persistent flows that need to coexist with other traffic flows. The Three-Tier architecture and current routing schemes are no longer sufficient for achieving high bandwidth utilization. Data center networks should be built in a way where they can adequately support virtualization and cloud computing technologies. Data center networks should provide services such as, simplified provisioning, workload mobility, dynamic routing and load balancing, equidistant bandwidth and latency. As data center networks have evolved the Three-Tier architecture has proven to be a challenge not only in terms of complexity and cost, but it also falls short of supporting many new data center applications. In this work we propose OneSwitch: A switch architecture for the data center. OneSwitch is backward compatible with current Ethernet standards and uses an OpenFlow central controller, a Location Database, a DHCP Server, and a Routing Service to build an Ethernet fabric that appears as one switch to end devices. This allows the data center to use switches in scale-out topologies to support hosts in a plug and play manner as well as provide much needed services such as dynamic load balancing, intelligent routing, seamless mobility, equidistant bandwidth and latency. / PHD / In the last two-decades data center networks have evolved to become a key element in improving levels of productivity and competitiveness for different types of organizations. Traditionally data center networks have been constructed with 3 layers of switches. This Three-Tier architecture has proven to be a challenge not only in terms of complexity and cost, but it also falls short of supporting many new data center applications. In this work we propose OneSwitch: A switch architecture for the data center. OneSwitch supports virtualization and cloud computing technologies by providing services such as, simplified provisioning, workload mobility, dynamic routing and load balancing, equidistant bandwidth and latency.

This thesis focuses on the study, implementation and improvement of a digital controller for a power factor correction (PFC) converter. The development of the telecommunications industry and the Internet demands reliable, cost-effective and intelligent power. Nowadays, the telecommunication power systems have output current of up to several kilo amperes, consisting of tens of modules. The high-end server system, which holds over 100 CPUs, consumes tens of kilowatts of power. For mission-critical applications, communication between modules and system controllers is critical for reliability. Information about temperature, current, and the total harmonic distortion (THD) of each module will enable the availability of functions such as dynamic temperature control, fault diagnosis and removal, and adaptive control, and will enhance functions such as current sharing and fault protection. The dominance of analog control at the modular level limits system-module communications. Digital control is well recognized for its communication ability. Digital control will provide the solution to system-module communication for the DC power supply. The PFC converter is an important stage for the distributed power system (DPS). Its controller is among the most complex with its three-loop structure and multiplier/divider. This thesis studies the design method, implementation and cost effectiveness of digital control for both a PFC converter and for an advanced PFC converter. Also discussed is the influence of digital delay on PFC performance. A cost-effective solution that achieves good performance is provided. The effectiveness of the solution is verified by simulation. The three level PFC with range switch is well recognized for its high efficiency. The range switch changes the circuit topology according to the input voltage level. Research literature has discussed the optimal control for both range-switch-off and range-switch-on topologies. Realizing optimal analog control requires a complex structure. Until now optimal control for the three-level PFC with analog control has not been achieved. Another disadvantage of the three-level PFC is the output capacitor voltage imbalance. This thesis proposes an active balancing solution to solve this problem. / Master of Science

Yes / Cloud fault tolerance is an important issue in cloud computing platforms and applications. In the event of an unexpected system failure or malfunction, a robust fault-tolerant design may allow the cloud to continue functioning correctly possibly at a reduced level instead of failing completely. To ensure high availability of critical cloud services, the application execution and hardware performance, various fault tolerant techniques exist for building self-autonomous cloud systems. In comparison to current approaches, this paper proposes a more robust and reliable architecture using optimal checkpointing strategy to ensure high system availability and reduced system task service finish time. Using pass rates and virtualised mechanisms, the proposed Smart Failover Strategy (SFS) scheme uses components such as Cloud fault manager, Cloud controller, Cloud load balancer and a selection mechanism, providing fault tolerance via redundancy, optimized selection and checkpointing. In our approach, the Cloud fault manager repairs faults generated before the task time deadline is reached, blocking unrecoverable faulty nodes as well as their virtual nodes. This scheme is also able to remove temporary software faults from recoverable faulty nodes, thereby making them available for future request. We argue that the proposed SFS algorithm makes the system highly fault tolerant by considering forward and backward recovery using diverse software tools. Compared to existing approaches, preliminary experiment of the SFS algorithm indicate an increase in pass rates and a consequent decrease in failure rates, showing an overall good performance in task allocations. We present these results using experimental validation tools with comparison to other techniques, laying a foundation for a fully fault tolerant IaaS Cloud environment.

O objetivo central desta investigação é demonstrar que a ponderação é racional. A proposição normativa particular concreta resultante de um caso de colisão de direitos fundamentais resolvido pela ponderação pode ser justificada racionalmente. O que se pretende sustentar é que o problema não está na ponderação, mas como ela é realizada para solucionar os casos de colisão de direitos fundamentais. A ponderação somente pode pretender racionalidade quando sustentada por razões dadas conforme regras. A proposição decisiva desta investigação é a de que a ponderação, como atividade argumentativa, deve observar as regras da argumentação racional. Essas regras são as regras da argumentação prática geral e da argumentação jurídica, formuladas pela teoria do discurso prático geral e do discurso jurídico. Elas configuram a base das regras próprias da ponderação racional. / The goal of this research is to show that balancing is rational. The particular concrete normative statement resulting from a collision of constitutional rights resolved by balancing can be justified rationally. The aim is to sustain that the problem is not balancing itself, but how it is used to solve the cases of collision of constitutional rights.The balancing can be rational only if supported by reasons given under rules. A crucial proposition of this research is that the balancing, as argumentative activity, must observe the rules of rational legal reasoning. These rules are the rules of the general practice argumentation and the rules of the legal reasoning, raised by the theory of general practical discourse and legal discourse. They make the basis of its own rules of rational balancing.

O objetivo central desta investigação é demonstrar que a ponderação é racional. A proposição normativa particular concreta resultante de um caso de colisão de direitos fundamentais resolvido pela ponderação pode ser justificada racionalmente. O que se pretende sustentar é que o problema não está na ponderação, mas como ela é realizada para solucionar os casos de colisão de direitos fundamentais. A ponderação somente pode pretender racionalidade quando sustentada por razões dadas conforme regras. A proposição decisiva desta investigação é a de que a ponderação, como atividade argumentativa, deve observar as regras da argumentação racional. Essas regras são as regras da argumentação prática geral e da argumentação jurídica, formuladas pela teoria do discurso prático geral e do discurso jurídico. Elas configuram a base das regras próprias da ponderação racional. / The goal of this research is to show that balancing is rational. The particular concrete normative statement resulting from a collision of constitutional rights resolved by balancing can be justified rationally. The aim is to sustain that the problem is not balancing itself, but how it is used to solve the cases of collision of constitutional rights.The balancing can be rational only if supported by reasons given under rules. A crucial proposition of this research is that the balancing, as argumentative activity, must observe the rules of rational legal reasoning. These rules are the rules of the general practice argumentation and the rules of the legal reasoning, raised by the theory of general practical discourse and legal discourse. They make the basis of its own rules of rational balancing.

O objetivo central desta investigação é demonstrar que a ponderação é racional. A proposição normativa particular concreta resultante de um caso de colisão de direitos fundamentais resolvido pela ponderação pode ser justificada racionalmente. O que se pretende sustentar é que o problema não está na ponderação, mas como ela é realizada para solucionar os casos de colisão de direitos fundamentais. A ponderação somente pode pretender racionalidade quando sustentada por razões dadas conforme regras. A proposição decisiva desta investigação é a de que a ponderação, como atividade argumentativa, deve observar as regras da argumentação racional. Essas regras são as regras da argumentação prática geral e da argumentação jurídica, formuladas pela teoria do discurso prático geral e do discurso jurídico. Elas configuram a base das regras próprias da ponderação racional. / The goal of this research is to show that balancing is rational. The particular concrete normative statement resulting from a collision of constitutional rights resolved by balancing can be justified rationally. The aim is to sustain that the problem is not balancing itself, but how it is used to solve the cases of collision of constitutional rights.The balancing can be rational only if supported by reasons given under rules. A crucial proposition of this research is that the balancing, as argumentative activity, must observe the rules of rational legal reasoning. These rules are the rules of the general practice argumentation and the rules of the legal reasoning, raised by the theory of general practical discourse and legal discourse. They make the basis of its own rules of rational balancing.

对于中国来说，对大国的渴望不再是这个问题，对邻近的东南亚国家实际上是有重大影响的。因此，近期国际关系奖学金已经引人注目的尝试，将“对冲”理念作为一种流行和根本的动态策略。本论文认为，越南对冲策略的选择是适当的，以便对付与中国的关系，但尚未完全保护越南的国家利益。本论文探讨了这一战略的四个关键组成部分：经济实用主义，硬平衡和软平衡。通过考虑和重新评估这些因素，研究发现了妨碍越南对冲实施的困难。此外，它还分析了大湄公河次区域（GMS）在经济领域的案例研究，以支持对经济实用主义的看法。最终得出结论，尽管越南在采取套期保值策略之后获得了一定的利益，但这些成就产生了国家安全的新风险，这可能会加剧该国在处理南海争端方面的压力。 / For China, the aspiration to great power no longer seems out of the question and this has actually a significant impact for neighboring Southeast Asian states. For this reason, there have been noticeable attempts in recent International Relations scholarship to introduce the concept of ‘hedging’ as a popular and fundamentally dynamic strategy for them. This thesis argues that the choice of Vietnam’s hedging strategy is appropriate so as to manage its relations with China, but has not yet protected Vietnam’s national interests completely. This thesis examines three of four key components of this strategy: economic pragmatism, hard balancing and soft balancing. By considering and reassessing these elements, the study finds difficulties that interfere in the implementation of Vietnam’s hedging. Furthermore, it incorporates an analysis of a case study in the economic realm, Greater Mekong Sub-region (GMS) in supporting the perceptions of economic pragmatism. Ultimately, it concludes that though Vietnam gains certain interests after adopting hedging strategy, those achievements produce new risks of national security that might increase more pressures for the country in dealing with the South China Sea (SCS) disputes.

Scheduling policies adopted for statistical multiplexing should provide delay differentiation between different traffic classes, where each class represents an aggregate traffic of individual applications having same target-queueing-delay requirements. We propose scheduling to optimally balance weighted mean instanteneous queue lengths and later weighted mean cumulative queue lengths as an approach to delay differentiation, where the class weights are set inversely proportional to the respective products of target delays and packet arrival rates. In particular, we assume a discrete-time, two-class, single-server queueing model with unit service time per packet and provide mathematical frame-work throughout our work. For iid Bernoulli packet arrivals, using a step-wise cost-dominance analytical approach using instantaneous queue lengths alone, for a class of one-stage cost functions not necessarily convex, we find the structure of the total-cost optimal policies for a part of the state space. We then consider two particular one-stage cost functions for finding two scheduling policies that are total-cost optimal for the whole state-space. The policy for the absolute weighted difference cost function minimizes the stationary mean, and the policy for the weighted sum-of-square cost function minimizes the stationary second-order moment, of the absolute value of the weighted difference of queue lengths. For the case of weighted sum-of-square cost function, the ‘iid Bernoulli arrivals’ assumption can be relaxed to either ‘iid arrivals with general batch sizes’ or to ‘Markovian zero-one arrivals’ for all of the state space, but for the linear switching curve. We then show that the average cost, starting from any initial state, exists, and is finite for every stationary work-conserving policy for our choices of the one-stage cost-function. This is shown for arbitrary number of class queues and for any i.i.d. batch arrival processes with finite appropriate moments. We then use cumulative queue lengths information in the one-step cost function of the optimization formulation and obtain an optimal myopic policy with 3 stages to go for iid arrivals with general batch sizes. We show analytically that this policy achieves the given target delay ratio in the long run under finite buffer assumption, given that feasibility conditions are satisfied. We take recourse to numerical value iteration to show the existence of average-cost for this policy. Simulations with varied class-weights for Bernoulli arrivals and batch arrivals with Poisson batch sizes show that this policy achieves mean queueing delays closer to the respective target delays than the policy obtained earlier. We also note that the coefficients of variation of the queueing delays of both the classes using cumulative queue lengths are of the same order as those using instantaneous queue lengths. Moreover, the short-term behaviour of the optimal myopic policy using cumulative queue lengths is superior to the existing standard policy reported by Coffman and Mitrani by a factor in the range of 3 to 8. Though our policy performs marginally poorer compared to the value-iterated, sampled, and then stationarily employed policy, the later lacks any closed-form structure. We then modify the definition of the third state variable and look to directly balance weighted mean delays. We come up with another optimal myopic policy with 3 stages to go, following which the error in the ratio of mean delays decreases as the window-size, as opposed to the policy mentioned in the last paragraph, wherein the error decreases as the square-root of the window-size. We perform numerical value-iteration to show the existence of average-cost and study the performance by simulation. Performance of our policy is comparable with the value-iterated, sampled, and then stationarily employed policy, reported by Mallesh. We have then studied general inter-arrival time processes and obtained the optimal myopic policy for the Pareto inter-arrival process, in particular. We have supported with simulation that our policy fares similarly to the PAD policy, reported by Dovrolis et. al., which is primarily heuristic in nature. We then model the possible packet errors in the multiplexed channel by either a Bernoulli process, or a Markov modulated Bernoulli process with two possible channel states. We also consider two possible round-trip-time values for control information, namely zero and one-slot. The policies that are next-stage optimal (for zero round-trip-time), and two-stage optimal (for one-slot round-trip-time) are obtained. Simulations with varied class-weights for Bernoulli arrivals and batch arrivals with Poisson batch sizes show that these policies indeed achieve mean queueing delays very close to the respective target delays. We also obtain the structure for optimal policies with N = 2 + ⌈rtt⌉ stages-to-go for generic values of rtt, and which need not be multiple of time-slots.

L'utilisation de systèmes de stockage de l'énergie électrique tels que les batteries nécessite l'assemblage de plusieurs cellules. Comme chacune de ces dernières peut avoir des caractéristiques légèrement différentes ainsi que des conditions d'environnement thermique ou de vieillissement distinctes, l'utilisation d'un système d'équilibrage permettant une bonne gestion de la répartition de l'énergie au sein des éléments qui composent le pack est nécessaire. Les travaux de recherche présentés se rapportent à l'étude et à la conception d'un tel circuit d'équilibrage à base de convertisseurs d'énergie intégrables ainsi qu'aux sollicitations électriques engendrées dans les cellules lors de son utilisation. / To store electrical energy in batteries, the use of multiple cells is needed. Since each of these cells can have slightly different characteristics and also different thermal or aging environmental conditions, a balancing system is required to manage the energy inside the battery pack. The researches described in this document show the study and the design of such a balancing system based on power electronics converters and also the impact of these systems on the electrochemical cells.