Maintaining closeness between data sources and data consumers is crucial for workload I/O performance. In cloud environments, this kind of closeness can be violated by system administrative events and storage architecture barriers. VM migration events are frequent in cloud environments. VM migration changes VM runtime inter-connection or cache contexts, significantly degrading VM I/O performance. Virtualization is the backbone of cloud platforms. I/O virtualization adds additional hops to workload data access path, prolonging I/O latencies. I/O virtualization overheads cap the throughput of high-speed storage devices and imposes high CPU utilizations and energy consumptions to cloud infrastructures. To maintain the closeness between data sources and workloads during VM migration, we propose Clique, an affinity-aware migration scheduling policy, to minimize the aggregate wide area communication traffic during storage migration in virtual cluster contexts. In host-side caching contexts, we propose Successor to recognize warm pages and prefetch them into caches of destination hosts before migration completion. To bypass the I/O virtualization barriers, we propose VIP, an adaptive I/O prefetching framework, which utilizes a virtual I/O front-end buffer for prefetching so as to avoid the on-demand involvement of I/O virtualization stacks and accelerate the I/O response. Analysis on the traffic trace of a virtual cluster containing 68 VMs demonstrates that Clique can reduce inter-cloud traffic by up to 40%. Tests of MPI Reduce_scatter benchmark show that Clique can keep VM performance during migration up to 75% of the non-migration scenario, which is more than 3 times of the Random VM choosing policy. In host-side caching environments, Successor performs better than existing cache warm-up solutions and achieves zero VM-perceived cache warm-up time with low resource costs. At system level, we conducted comprehensive quantitative analysis on I/O virtualization overheads. Our trace replay based simulation demonstrates the effectiveness of VIP for data prefetching with ignorable additional cache resource costs.

To leverage the elastic resource allocation of cloud computing and enhance the service availability and productivity, numerous applications and businesses have been moved from the traditional data centers into the cloud during the past decade. Despite the benefits introduced by virtualization, such as high resource utilization, flexible resource management and operation cost reduction, it also incurs additional overhead, scheduling delays as well as semantic gaps among hardware, operating system and applications. These issues can cause non-negligible impact to the performance and quality-of-service (QoS) of the cloud applications, especially for I/O-intensive services. Meanwhile, the increasing scale and complexity of the cloud infrastructure aggravate the above problems, making both characterization and optimization of the virtualized network performance much more difficult. In this dissertation, we explore the potential opportunities in various cloud infrastructures including the traditional virtual machines (VM), emerging containers as well as the application runtime, and present lightweight and efficient approaches to characterize and optimize the network performance in virtualized environments. From the perspective of characterization in virtualized networks, we designed and developed an in-band packet profiler, namely Time Capsule, which traced packet level granularity latency across different boundaries in virtualized systems with negligible overhead.By leveraging the superpower of extended Berkeley Packet Filter (eBPF), we proposed vNetTracer, a highly efficient and programmable profiler to trace application network performance in virtualized networks. Both Time Capsule and vNetTracer shed light on the virtualized network monitoring and can help users analyze, identify and localize potential issues inside virtualized networks. Besides the above tools, we also investigated the existing virtualized networks inside the containers and performed a comprehensive study of representative container networks. Our study illustrated many important findings that could help users select the appropriate network for their workloads and guide the optimization of the existing container networks. From the perspective of optimization in virtualized networks, we proposed and developed several approaches for improving the performance of I/O-intensive applications invirtualized environments. We investigated the sub optimal I/O performance of applications in the VMs or containers, and discovered the CPU discontinuity caused priority inversions and rendered existing I/O prioritization in the guest OS ineffective. Thus, we proposed xBalloon, a lightweight approach to preserving static and dynamic priorities between I/O bound and compute-bound tasks and boosting the I/O performance under discontinuous time. We also presented an in-depth performance analysis of the Java virtual machine(JVM) and found the existing design of JVM incurred inefficient garbage collection, which introduced the low throughput and long tail latency of the applications. To mitigate the overhead, we propose a number of solutions to these issues, including enforcing GC thread affinity to aid multicore load balancing and designing a more efficient work stealing algorithm. We implemented and evaluated the above techniques in both local lab clusters and public cloud with representative benchmark suites. The experiment results and case studies demonstrated the effectiveness of our proposed techniques. The main contribution of this dissertation lied in simple yet effective solutions that characterize and improve the network performance in various virtualized environments of the cloud.

First, we introduce the Workload-Aware IO Outsourcing scheme, called WAIO, to improve the VM live storage migration efficiency. Second, we address this problem by proposing a novel scheme, called SnapMig, to improve the VM live storage migration efficiency and eliminate its performance impact on user applications at the source server by effectively leveraging the existing VM snapshots in the backup servers. Third, we propose the IOFollow scheme to improve both the VM performance and migration performance simultaneously. Finally, we outline the direction for the future research work.

One of the major developments in the computing field has been cloud computing, which enables users to do complicated computations that local devices are unable to handle. The computing power and flexibility that have made the cloud so popular do not come without challenges. It is particularly challenging to decide which resources to use, even when they have the same configuration but different levels of performance because of the variable structure of the available resources. Cloud data centers can host millions of virtual machines, and where to locate these machines in the cloud is a difficult problem. Additionally, fulfilling optimization needs is a complex problem. Reliable and Intelligent Optimization in Multi-Layered Cloud Computing Architectures examines ways to meet these challenges. It discusses virtual machine placement techniques and task scheduling techniques that optimize resource utilization and minimize energy consumption of cloud data centers. Placement techniques presented can provide an optimal solution to the optimization problem using multiple objectives. The book focuses on basic design principles and analysis of virtual machine placement techniques and task allocation techniques. It also looks at virtual machine placement techniques that can improve quality-of-service (QoS) in service-oriented architecture (SOA) computing. The aims of virtual machine placement include minimizing energy usage, network traffic, economical cost, maximizing performance, and maximizing resource utilization. Other highlights of the book include: Improving QoS and resource efficiency Fault-tolerant and reliable resource optimization models A reactive fault tolerance method using checkpointing restart Cost and network-aware metaheuristics. Virtual machine scheduling and placement Electricity consumption in cloud data centers Written by leading experts and researchers, this book provides insights and techniques to those dedicated to improving cloud computing and its services.

This book focuses on the current trends in research and analysis of virtual machine placement in a cloud data center. It discusses the integration of machine learning models and metaheuristic approaches for placement techniques. Taking into consideration the challenges of energy-efficient resource management in cloud data centers, it emphasizes upon computing resources being suitably utilised to serve application workloads in order to reduce energy utilisation, while maintaining apt performance. This book provides information on fault-tolerant mechanisms in the cloud and provides an outlook on task scheduling techniques. Focuses on virtual machine placement and migration techniques for cloud data centers Presents the role of machine learning and metaheuristic approaches for optimisation in cloud computing services Includes application of placement techniques for quality of service, performance, and reliability improvement Explores data center resource management, load balancing and orchestration using machine learning techniques Analyses dynamic and scalable resource scheduling with a focus on resource management The text is for postgraduate students, professionals, and academic researchers working in the fields of computer science and information technology.

The purpose of this book is first to study cloud computing concepts, security concern in clouds and data centers, live migration and its importance for cloud computing, the role of firewalls in domains with particular focus on virtual machine (VM) migration and its security concerns. The book then tackles design, implementation of the frameworks and prepares test-beds for testing and evaluating VM migration procedures as well as firewall rule migration. The book demonstrates how cloud computing can produce an effective way of network management, especially from a security perspective.

Networking and machine virtualization play critical roles in the success of modern cloud computing. The energy consumption of physical machines has been carefully examined in the past, including the impact from network traffic. When it comes to virtual machines (VMs) in cloud data centers, it remains unexplored how the highly dynamic traffic affects the energy consumption in virtualized environments. In this thesis, we first present an empirical study on the interplay between energy consumption and network transactions in virtualized environments. Through the real-world measurement on both Xen- and KVM-based platforms, we show that these state-of-the-art designs bring significant overhead on virtualizing network devices and noticeably increase the demand of CPU resources when handling network traffic. Furthermore, the energy consumption varies significantly with traffic allocation strategies and virtual CPU affinity conditions, which was not seen in conventional physical machines. Next, we study the performance and energy efficiency issues when CPU intensive tasks and I/O intensive tasks are co-located inside a VM. A combined effect from device virtualization overhead and VM scheduling latency can cause severe interference in the presence of such hybrid workloads. To this end, we propose Hylics, a novel solution that enables an efficient data traverse path for both I/O and computation operations, and decouples the costly interference. Several important design issues are pinpointed and addressed during our implementation, including efficient intermediate data sharing, network service offloading, and QoS-aware memory usage management. Based on our real-world deployment in KVM, Hylics can improve computation and networking performance with a moderate amount of memory usage. Moreover, this design also sheds new light on optimizing the energy efficiency for virtualized systems.