Data centres and other infrastructures in the field of information technology suffer from the major issue of ‘server sprawl’, a term used to depict the situation wherein a number of servers consume resources inefficiently, when compared to the business value of outcome obtained from them. Consolidation of servers, rather than dedicating whole servers to individual applications, optimizes the usage of hardware resources, and virtualization achieves this by allowing multiple servers to share a single hardware platform. Server virtualization is facilitated by the usage of hypervisors, among which Xen is widely preferred because of its dual virtualization modes, virtual machine migration support and scalability. This research work involves an analysis of the CPU scheduling algorithms incorporated into Xen, on the basis of the algorithm’s performance in different workload scenarios. In addition to performance evaluation, the results obtained lay emphasis on the importance of compute intensive or I/O intensive domain handling capacity of a hypervisor’s CPU scheduling algorithm in virtualized server environments. Based on this knowledge, the selection of CPU scheduler in a hypervisor can be aligned with the requirements of the hosted applications. A new credit-based VCPU scheduling scheme is proposed, in which the credits remaining for each VCPU after every accounting period plays a significant role in the scheduling decision. The proposed scheduling strategy allows those VCPUs of I/O intensive domains to supersede others, in order to favour the reduction of I/O bound domain response times and the subsequent bottleneck in the CPU run queue. Though a small percentage of context switch overhead is introduced, the results indicate substantial improvement of I/O handling and fairness in re-source allocation between the host and guest domains.

This thesis discusses the increasing performance of Platform as a Service using virtualiza-tion. It focuses on the new trends in the provision of IT services, which is virtualization. Possibility of huge savings and improvement of performance of the hardware is interesting for every company, that's why a lot of companies want to migrate to the vir-tual infrastructure. The first part defines IT service and its categories. It describes the development of IT service and brings definitions based on multiple resources. The second part characterizes cloud computing services. This part focuses on the actual composition of the various forms of technology deployments and distribution models. Further focuses on the main benefits and disadvantages of the types of cloud computing. The focus of third part is virtualization. This part presents a five-step procedure for that matter the transition to virtualization. Chapter helps to understand the value that may pose to the enterprise virtualization. The fourth section deals with virtualization in a particular environment. This part brings specific solution of infrastructure virtualization together with the creation of the virtual machine for a new user.

The aim of this master's thesis is to select a suitable option to replace outdated hardware equipment of the company RR Donnelley Prague s.r.o.. In the theoretical part, terms 'virtualization', 'cloud' and their models are explained. Next, RR Donnelley Prague is described and the current situation in terms of hardware infrastructure and outsourced services is analysed. The practical part contains a recommendation of possible solutions of the situation described and, particularly, a selection of criteria assessed and a multi-criteria evaluation of proposed solutions. To estimate weights of the criteria, a scoring method and a paired comparison method is applied. The multi-criteria evaluation of options uses the weighted sum method and TOPSIS. In the end, results of the applied methods are compared and benefits of the thesis for the company and the author are quantified.

The Diploma thesis analyzes the attitude of small and medium Czech enterprises towards the Green IT and sustainability concept. Several practices such as consolidation and virtualization of servers, desktop virtualization, cloud computing, energy management, dematerialization and recycling are discussed with regards to their contribution to global sustainability. The common denominator of most of the Green IT practices is the energy consumption reduction. The increasing information technology's demand for energy is viewed as a major contributor to the global carbon footprint and Green IT practices are assessed in terms of how much energy can be saved by incorporating them in a company policy. Besides energy consumption material aspects are another significant part of Green IT. Both the toxicity of certain materials used in the manufacturing process and the increased need for proper recycling of electronic waste are discussed in respective chapters. Information technology does not only add to the global carbon footprint, but it can also provide means to reduce the emissions of other sectors. Companies can reduce their energy consumption by improving logistics (smart logistics) or buildings (smart buildings) efficiency. Teleworking is another practice which enables millions of people work outside their office and contributes to global sustainability. The analytical part presents a survey of Czech small and medium enterprises and their attitude to Green IT. The main objective of the survey is to find out how many companies have implemented Green IT into their company policy. Company representatives report on which Green IT practices they have adopted and why. Responses are analyzed and findings and conclusions are presented.

Orientadores: Eduardo Cândido Xavier, Nelson Luis Saldanha da Fonseca / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-24T12:31:15Z (GMT). No. of bitstreams: 1 Silva_IgorRosbergdeMedeiros_M.pdf: 1354578 bytes, checksum: 029116a11f51931ed73b6b4b5c6d6ff9 (MD5) Previous issue date: 2014 / Resumo: Virtualização de Redes tem recebido recentemente atenção da comunidade científica, uma vez que ela provê mecanismos para lidar com o problema da ossificação da atual arquitetura da Internet. Através da decomposição de Provedores de Serviço de Internet em Provedores de Infraestrutura e Provedores de Serviço, a Virtualização de Redes permite que várias redes virtuais heterogêneas compartilhem o mesmo substrato físico. Um dos principais problemas relacionados à Virtualização de Redes é o Problema do Mapeamento de Redes Virtuais no substrato, que é NP-Difícil. Muitos algoritmos e heurísticas para encontrar bons mapeamentos, de modo a otimizar o uso da banda passante na rede física, têm sido propostos. Neste trabalho, apresentam-se dois novos algoritmos baseados na metaheurística Busca Tabu, o VNE-TS e o VNE-TS-Clustering. Propõe-se também um algoritmo de seleção de redes virtuais, o 2ks-VN-Selector, que se baseia no Problema da Mochila Bidimensional, cujo objetivo é aumentar o rendimento em Provedores de Infraestrutura. Os resultados obtidos pelos uso das heurísticas VNE-TS e VNE-TS-Clustering, são comparandos com os resultados obtidos pelo algoritmo VNE-PSO,uma das melhores heurísticas de mapeamento proposta na literatura para o Problema do Mapeamento de Redes Virtuais. São comparados, também, os resultados da política de seleção 2ks-VN-Selector com os obtidos pela política Most Prize First. Resultados mostram tanto VNE-TS quanto VNE-TS-Clustering rejeitam menos requisições do que o VNE-PSO e que o algoritmo de seleção 2ks-VN-Selector é capaz de aumentar o rendimento de Provedores de Infraestrutura em relação ao algoritmo Most Prize First / Abstract: In recent years, network virtualization has gained considerable attention from the scientific community, since it provides mechanisms to overcome the ossification problem of the current Internet architecture. Through separation of Internet Service Providers into Infrastructure Providers and Service Providers, network virtualization allows multiple heterogeneous virtual networks to share the same physical substrate. One of the main problems regarding network virtualization is the Network Embedding Problem, which is NP-Hard. Several algorithms and heuristics to find a set of good mappings that optimize the use of the bandwidth in substrate networks have been proposed. In this work, we present two new embedding heuristics based on the Tabu Search metaheuristic: the VNE-TS and VNE-TS-Clustering. We also propose a virtual network selection policy, the 2ks-VN-Selector, based on the Bidimensional Knapsack Problem, which aims to increase the profit of Infrastructure Providers. We compare the results obtained by using the VNE-TS and VNE-TS-Clustering heuristics, to those obtained by using the VNE-PSO, one of the best heuristics proposed in the literature for the Embedding Problem. We also compare the effects of the 2ks-VN-Selector with those obtained by using another well known selection policy: Most Prize First. Results show that both VNE-TS and VNE-TS-Clustering reject less virtual network requests than VNE-PSO and that the selection algorithm 2ks-VN-Selector is able to increase the profit of Infrastructure Providers when compared to the Most Prize First algorithm / Mestrado / Ciência da Computação / Mestre em Ciência da Computação

Cette thèse s'inscrit dans le contexte de la désagrégation des systèmes informatiques - une approche novatrice qui devrait gagner en popularité dans le secteur des centres de données. A la différence des systèmes traditionnels en grappes, où les ressources sont fournies par une ou plusieurs machines, dans les systèmes désagrégés les ressources sont fournies par des nœuds discrets, chaque nœud ne fournissant qu'un seul type de ressources (unités centrales de calcul, mémoire, périphériques). Au lieu du terme de machine, le terme de créneau (slot) est utilisé pour décrire une unité de déploiement de charge de travail. L'emplacement est assemblé dynamiquement avant un déploiement de charge de travail par l'orchestrateur système.Dans l'introduction nous abordons le sujet de la désagrégation et en présentons les avantages par rapport aux architectures en grappes. Nous ajoutons également au tableau une couche de virtualisation car il s'agit d'un élément crucial des centres de données. La virtualisation fournit une isolation entre les charges de travail déployées et un partitionnement flexible des ressources. Elle doit cependant être adaptée afin de tirer pleinement parti de la désagrégation. C'est pourquoi les principales contributions de ce travail se concentrent sur la prise en charge de la couche de virtualisation pour la mémoire désagrégée et la mise à disposition des périphériques.La première contribution principale présente les modifications de la pile logicielle liées au redimensionnement flexible de la mémoire d'une machine virtuelle (VM). Elles permettent d'ajuster la quantité de RAM hébergée (c'est à dire utilisée par la charge de travail en cours d'exécution dans une VM) pendant l'exécution avec une granularité d'une section mémoire. Du point de vue du logiciel il est transparent que la RAM proviennent de banques de mémoire locales ou distantes.La deuxième contribution discute des notions de partage de mémoire entre machines virtuelles et de migration des machines virtuelles dans le contexte de la désagrégation. Nous présentons d'abord comment des régions de mémoire désagrégées peuvent être partagées entre des machines virtuelles fonctionnant sur différents nœuds. De plus, nous discutons des différentes variantes de la méthode de sérialisation des accès simultanés. Nous expliquons ensuite que la notion de migration de VM a acquis une double signification avec la désagrégation. En raison de la désagrégation des ressources, une charge de travail est associée au minimum à un nœud de calcul et a un nœud mémoire. Il est donc possible qu'elle puisse être migrée vers des nœuds de calcul différents tout en continuant à utiliser la même mémoire, ou l'inverse. Nous discutons des deux cas et décrivons comment cela peut ouvrir de nouvelles opportunités pour la consolidation des serveurs.La dernière contribution de cette thèse est liée à la virtualisation des périphériques désagrégés. Partant de l'hypothèse que la désagrégation de l'architecture apporte de nombreux effets positifs en général, nous expliquons pourquoi elle n'est pas immédiatement compatible avec la technique d'attachement direct, est pourtant très populaire pour sa performance quasi native. Pour remédier à cette limitation, nous présentons une solution qui adapte le concept d'attachement direct à la désagrégation de l'architecture. Grâce à cette solution, les dispositifs désagrégés peuvent être directement attachés aux machines virtuelles, comme s'ils étaient branchés localement. De plus, l'OS hébergé, pour lequel la configuration de l'infrastructure sous-jacente n'est pas visible, n'est pas lui-même concerné par les modifications introduites. / This dissertation is positioned in the context of the system disaggregation - a novel approach expected to gain popularity in the data center sector. In traditional clustered systems resources are provided by one or multiple machines. Differently to that, in disaggregated systems resources are provided by discrete nodes, each node providing only one type of resources (CPUs, memory and peripherals). Instead of a machine, the term of a slot is used to describe a workload deployment unit. The slot is dynamically assembled before a workload deployment by the unit called system orchestrator.In the introduction of this work, we discuss the subject of disaggregation and present its benefits, compared to clustered architectures. We also add a virtualization layer to the picture as it is a crucial part of data center systems. It provides an isolation between deployed workloads and a flexible resources partitioning. However, the virtualization layer needs to be adapted in order to take full advantage of disaggregation. Thus, the main contributions of this work are focused on the virtualization layer support for disaggregated memory and devices provisioning.The first main contribution presents the software stack modifications related to flexible resizing of a virtual machine (VM) memory. They allow to adjust the amount of guest (running in a VM) RAM at runtime on a memory section granularity. From the software perspective it is transparent whether they come from local or remote memory banks.As a second main contribution we discuss the notions of inter-VM memory sharing and VM migration in the disaggregation context. We first present how regions of disaggregated memory can be shared between VMs running on different nodes. This sharing is performed in a way that involved guests which are not aware of the fact that they are co-located on the same computing node or not. Additionally, we discuss different flavors of concurrent accesses serialization methods. We then explain how the VM migration term gained a twofold meaning. Because of resources disaggregation, a workload is associated to at least one computing node and one memory node. It is therefore possible that it is migrated to a different computing node and keeps using the same memory, or the opposite. We discuss both cases and describe how this can open new opportunities for server consolidation.The last main contribution of this dissertation is related to disaggregated peripherals virtualization. Starting from the assumption that the architecture disaggregation brings many positive effects in general, we explain why it breaks the passthrough peripheral attachment technique (also known as a direct attachment), which is very popular for its near-native performance. To address this limitation we present a design that adapts the passthrough attachment concept to the architecture disaggregation. By this novel design, disaggregated devices can be directly attached to VMs, as if they were plugged locally. Moreover, all modifications do not involve the guest OS itself, for which the setup of the underlying infrastructure is not visible.

Fog computing is a distributed computing paradigm that brings data processing from remote cloud data centers into the vicinity of the edge of the network. The computation is performed closer to the source of the data, and thus it decreases the time unpredictability of cloud computing that stems from (i) the computation in shared multi-tenant remote data centers, and (ii) long distance data transfers between the source of the data and the data centers. The computation in fog computing provides fast response times and enables latency sensitive applications. However, industrial systems require time-bounded response times, also denoted as RT. The correctness of such systems depends not only on the logical results of the computations but also on the physical time instant at which these results are produced. Time-bounded responses in fog computing are attributed to two main aspects: computation and communication.    In this thesis, we explore both aspects targeting soft RT applications in fog computing in which the usefulness of the produced computational results degrades with real-time requirements violations. With regards to the computation, we provide a systematic literature survey on a novel lightweight RT container-based virtualization that ensures spatial and temporal isolation of co-located applications. Subsequently, we utilize a mechanism enabling RT container-based virtualization and propose a solution for orchestrating RT containers in a distributed environment. Concerning the communication aspect, we propose a solution for a dynamic bandwidth distribution in virtualized networks.

The purpose of master’s thesis is to project virtualization solution together with replication of the servers. Thesis is divided into the three parts and that it theoretical, analytical and projection part. In analytical part there are basic information about virtualization technologies, in analytical part there is analysis of the present status of the company and mainly about status of the IT infrastructure and in the end projection part there is realization of the virtualization solution from choosing the right type of cluster to choosing hardware solution.

In this dissertation, we have analyzed various security and trustworthy solutions for modern computing systems and proposed a framework that will provide holistic security and trust for the entire lifecycle of a virtualized workload. The framework consists of 3 novel techniques and a set of guidelines. These 3 techniques provide necessary elements for secure and trusted execution environment while the guidelines ensure that the virtualized workload remains in a secure and trusted state throughout its lifecycle. We have successfully implemented and demonstrated that the framework provides security and trust guarantees at the time of launch, any time during the execution, and during an update of the virtualized workload. Given the proliferation of virtualization from cloud servers to embedded systems, techniques presented in this dissertation can be implemented on most computing systems.

Migrer à chaud une machine virtuelle (VM) est une opération basique dans un centre de données. Tous les jours, des VM sont migrées pour répartir la charge, économiser de l'énergie ou préparer la maintenance de serveurs. Bien que les problèmes de placement des VM soient beaucoup étudiés, on observe que la gestion des migrations permettant de transiter vers ces nouveaux placements reste un domaine de second plan. Cette phase est cependant critique car chaque migration à un coût en terme de CPU, de bande passante et d'énergie. Des algorithmes de décision reposent alors sur des hypothèses irréalistes et calculent des ordonnancements conduisant à des migrations longues et incontrôlables qui réduisent les bénéfices attendus de la ré-organisation des VM.Dans cette thèse nous nous sommes fixé comme objectif d'améliorer la qualité des ordonnancements de migrations dans les centres de données. Pour cela, nous avons d'abord modélisé l'ordonnancement de migrations en considérant l'architecture réseau et l'activité mémoire des VM. Pour évaluer l'efficacité de notre modèle, nous avons ensuite implémenté un ordonnanceur de migrations au sein du gestionnaire de VM BtrPlace. Nous avons ensuite étendu notre ordonnanceur en développant des contraintes d'ordonnancement, des objectifs personnalisés, une heuristique de recherche ainsi qu'un modèle énergétique.Nous avons validé notre approche par l'étude pratique de scénarios d'ordonnancement réalisés en environnement réel. Nous avons ainsi pu analyser la précision de notre modèle de migration, valider la qualité des décisions prises par notre modèle d'ordonnancement et évaluer l'extensibilité ainsi que le passage à l'échelle de notre solution / A live-migration of a virtual machine (VM) is a basic operation in a data center. Every day, VMs are migrated to distribute the load, save energy or prepare maintenance operations on production servers. Although VM placement problems have been extensively studied, we observe that the migrations management needed to apply these new placements did not get much attention. This phase is however critical as each migration has a cost in terms of CPU, bandwidth and energy. Decision algorithms are thus based on unrealistic assumptions and compute schedules which can lead to unnecessarily long and uncontrollable migrations. This reduces the ultimate benefits expected from the VMs re-organization.In this thesis, our main ojective is to improve the efficiency of live-migrations scheduling within data centers. To achieve our goal, we have first modeled the scheduling of live migrations based on the network architecture and the VMs memory activity. To evaluate the efficiency of our model, we have then implemented and optimized a migrations scheduler within the VMs manager BtrPlace. We have then extended our scheduler by developing scheduling constraints, custom objectives, a search heuristic and an energy model.We have validated our approach by the practical study of many scheduling scenarios executed in a real environment. We have then analyzed the accuracy of our migration model, assessed the quality of the decisions taken by our scheduling model, and evaluated the extensibility and the scalability of our solution