Ravi Jhawar

Fault Tolerance Management in Cloud Computing: A System-Level Perspective

The increasing popularity of Cloud computing as an attractive alternative to classic information processing systems has increased the importance of its correct and continuous operation even in the presence of faulty components. In this paper, we introduce an innovative, system-level, modular perspective on creating and managing fault tolerance in Clouds. We propose a comprehensive high-level approach to shading the implementation details of the fault tolerance techniques to application developers and users by means of a dedicated service layer. In particular, the service layer allows the user to specify and apply the desired level of fault tolerance, and does not require knowledge about the fault tolerance techniques that are available in the envisioned Cloud and their implementations.

Supporting Security Requirements for Resource Management in Cloud Computing

We address the problem of guaranteeing security, with additional consideration on reliability and availability issues, in the management of resources in Cloud environments. We investigate and formulate different requirements that users or service providers may wish to specify. Our framework allows providers to impose restrictions on the allocations to be made to their hosts and users to express constraints on the placement of their virtual machines (VMs). Users placement constraints may impose restrictions in performing allocation to specific locations, within certain boundaries, or depending on some conditions (e.g., requiring a VM to be allocated to a different host wrt other VMs). Our approach for VM allocation goes beyond the classical (performance/cost-oriented) resource consumption to incorporate the security requirements specified by users and providers.

Fault tolerance management in IaaS clouds

Fault tolerance, reliability and availability in Cloud computing are critical to ensure correct and continuous system operation also in the presence of failures. In this paper, we present an approach to evaluate fault tolerance mechanisms that use the virtualization technology to transparently increase the reliability and availability of applications deployed in the virtual machines in a Cloud. In contrast to several existing solutions that assume independent failures, we take into account the failure behavior of various server components, network and power distribution in a typical Cloud computing infrastructure, the correlation between individual failures, and the impact of each failure on users applications. We use this evaluation to study fault tolerance mechanisms under different deployment contexts, and use it as the basis to develop a methodology for identifying and selecting mechanisms that match users fault tolerance requirements.

Fault Tolerance and Resilience in Cloud Computing Environments

The increasing demand for flexibility and scalability in dynamically obtaining and releasing computing resources in a cost-effective and device-independent manner, and easiness in hosting applications without the burden of installation and maintenance, has resulted in a wide adoption of the cloud computing paradigm. While the benefits are immense, this computing paradigm is still vulnerable to a large number of system failures; as a consequence, users have become increasingly concerned about the reliability and availability of cloud computing services. Fault tolerance and resilience serve as an effective means to address users’ reliability and availability concerns. In this chapter, we focus on characterizing the recurrent failures in a typical cloud computing environment, analyzing the effects of failures on users’ applications and surveying fault tolerance solutions corresponding to each class of failures. We also discuss the perspective of offering fault tolerance as a service to users’ applications as one of the effective means of addressing users’ reliability and availability concerns.

Reliable mission deployment in vulnerable distributed systems

Recent years have seen a growing interest in mission-centric operation of large-scale distributed systems. However, due to their complexity, these systems are prone to failures and vulnerable to a wide range of cyber-attacks. Current solutions focus either on the infrastructure itself or on mission analysis, but fail to consider information about the complex interdependencies existing between system components and mission tasks. In this paper, we take a different approach, and present a solution for deploying mission tasks in a distributed computing environment in a way that minimizes a missions exposure to vulnerabilities by taking into account available information about vulnerabilities and dependencies. We model the mission deployment problem as a task allocation problem, subject to various dependability constraints. The proposed solution is based on the A* algorithm for searching the solution space, but we also introduce a heuristic to significantly improve the search performance. We validate our approach, and show that our algorithm scales linearly with the size of both missions and networks.

Dependability certification of services: a model-based approach

The advances and success of the Service-Oriented Architecture (SOA) paradigm have produced a revolution in ICT, particularly, in the way in which software applications are implemented and distributed. Today, applications are increasingly provisioned and consumed as web services over the Internet, and business processes are implemented by dynamically composing loosely coupled applications provided by different suppliers. In this highly dynamic context, clients (e.g., business owners or users selecting a service) are concerned about the dependability of their services and business processes. In this paper, we define a certification scheme that allows to verify the dependability properties of services and business processes. Our certification scheme relies on discrete-time Markov chains and awards machine-readable dependability certificates to services, whose validity is continuously verified using run-time monitoring. Our solution can be integrated within existing SOAs, to extend the discovery and selection process with dependability requirements and certificates, and to support a dependability-aware service composition.

Securing Mission-Centric Operations in the Cloud

Recent years have seen a growing interest in the use of Cloud Computing facilities to execute critical missions. However, due to their inherent complexity, most Cloud Computing services are vulnerable to multiple types of cyber-attacks and prone to a number of failures. Current solutions focus either on the infrastructure itself or on mission analysis, but fail to consider the complex interdependencies between system components, vulnerabilities, failures, and mission tasks. In this chapter, we propose a different approach, and present a solution for deploying missions in the cloud in a way that minimizes a mission’s exposure to vulnerabilities by taking into account available information about vulnerabilities and dependencies. We model the mission deployment problem as a task allocation problem, subject to various dependability constraints, and propose a solution based on the A ∗ algorithm for searching the solution space. Additionally, in order to provide missions with further availability and fault tolerance guarantees, we propose a cost-effective approach to harden the set of computational resources that have been selected for executing a given mission. Finally, we consider offering fault tolerance as a service to users in need of deploying missions in the Cloud. This approach allows missions to obtain required fault tolerance guarantees from a third party in a transparent manner.

Chapter 1 – Fault Tolerance and Resilience in Cloud Computing Environments

The increasing demand for flexibility and scalability in dynamically obtaining and releasing computing resources in a cost-effective and device-independent manner, and easiness in hosting applications without the burden of installation and maintenance, has resulted in a wide adoption of the cloud computing paradigm. While the benefits are immense, this computing paradigm is still vulnerable to a large number of system failures; as a consequence, users have become increasingly concerned about the reliability and availability of cloud computing services. Fault tolerance and resilience serve as an effective means to address users’ reliability and availability concerns. In this chapter, we focus on characterizing the recurrent failures in a typical cloud computing environment, analyzing the effects of failures on users’ applications and surveying fault tolerance solutions corresponding to each class of failures. We also discuss the perspective of offering fault tolerance as a service to users’ applications as one of the effective means of addressing users’ reliability and availability concerns.

Dependability-Oriented Resource Management Schemes for Cloud Computing Data Centers

A major factor in the growth of the Information and Communications Technology has been the widespread use of data centers for deploying and executing web services, business processes, and scientific and e-commerce applications. While some data centers are designed to operate a specific business (e.g., Google’s search engine), others are used as the backbone infrastructure to deliver computing resources as services to hundreds of users (e.g., Amazon’s EC2 service). Relying on data centers for running applications, particularly when resources are delivered to the users as a service, offer significant benefits. For example, applications can benefit significantly from the economy of scale, and users are relieved from buying expensive hardware and software licenses and from maintaining the computing infrastructure.