A²thOS: availability analysis and optimisation in SLAs

Abstract

SUMMARYIT service availability is at the core of customer satisfaction and business success for today's organisations. Many medium-large size organisations outsource part of their IT services to external providers, with Service Level Agreements describing the agreed availability of outsourced service components. Availability management of partially outsourced IT services is a non trivial task since classic approaches for calculating availability are not applicable, and IT managers can only rely on their expertise to fulfil it. This often leads to the adoption of non optimal solutions. In this paper we present A 2 THOS, a framework to calculate the availability of partially outsourced IT services in the presence of SLAs and to achieve a cost-optimal choice of availability levels for outsourced IT components while guaranteeing a target availability level for the service.

Using Bayesian networks for highly available cloud-based web applications

“…The work of Zambon et al presents many similarities to the approach here proposed [25]; the main differences are: (1) the approach proposed here tries to overcome the limitations of the formalisms used in [25] (i.e., fault trees and reliability block diagrams); (2) the perspective of the approach here proposed is not limited to planning activities but also to monitoring and enforcement actions; (3) the proposed approach is user oriented. While other approaches focus on traditional straight-forward software development [26], in this work, model-driven principles and techniques are chosen to raise the level of abstraction and to improve the participation of the stakeholders in all phases of the cloud service life cycle.…”