A Migration Approach for Fault Tolerance in Cloud Computing

Introduction

Most Cloud computing can be defined as a new style of computing in which dynamically scalable and often virtualized resources are provided as a services over the internet. Cloud computing has become a significant technology trend, and many experts expect that cloud computing will reshape information technology (IT) processes and the IT marketplace. With the cloud computing technology, users use a variety of devices, including PCs, laptops, smartphones, and PDAs to access programs, storage, and application-development platforms over the internet, via services offered by cloud computing providers. It provides the illusion of availability of unlimited resources to fulfill dynamic and variable user requirements. Advantages of the cloud computing technology include cost savings, high availability, and easy scalability (Aljawarneh, 2011; Kaushal & Bala, 2011; Arshad et al., 2012).

Cloud computing takes the technology, services, and applications that are similar to those on the Internet and turns them into a self-service utility. The use of the word “cloud” makes reference to the two essential concepts:

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  Abstraction: Cloud computing abstracts the details of system implementation from users and developers. Applications run on physical systems that aren't specified, data is stored in locations that are unknown, administration of systems is outsourced to others, and access by users is ubiquitous;

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  Virtualization: Cloud computing virtualizes systems by pooling and sharing resources. Systems and storage can be provisioned as needed from a centralized infrastructure, costs are assessed on a metered basis, multi-tenancy is enabled, and resources are scalable with agility (Sosinsky, 2011).

Virtualization techniques are commonly used in cloud platforms to implement partitioning of resources. Instead of having direct access to cloud resources, customers have access to virtual machines, which represent a fraction of a physical machine. Then, we identify three layers in such a cloud infrastructure: the physical resource layer (containing the overall cloud resources), the virtualization layer (containing virtual machines) and the applications layer (containing applications of external companies, which are hosted in the cloud) (Tchana et al., 2012).

The reliability of Cloud computing still remains a major concern among users. Due to economic pressures, these computing infrastructures often use commodity components exposing the hardware to scale and conditions for which it was not originally designed (Vishwanath & Nagappan, 2010). As a result, significantly large numbers of failures manifests in the system and seemingly impose high implications on the hosted applications, impacting their availability and performance. For example, Amazon’s Elastic Compute Cloud (EC2) experienced failure in Elastic Block Storage (EBS) drives and network configuration (“Amazon Elastic Compute Cloud,”) bringing down thousands of hosted applications and websites for 3 days and 3 hours (“Summary of the Amazon EC2”). Table 1 shows failover records from some of the cloud service provider system.