End-to-end Resiliency Analysis Framework for Cloud Storage Services

Cloud storage services are becoming increasingly complex with the stored data volume and operational scale. The complexity is the result of the ever-growing components with various functionalities being involved for service rendition, exposing the service to numerous failures or disruptions. In such scenarios, resiliency becomes one of the most crucial parameters to evaluate how well-equipped the system is to withstand the effect of disruptions and maintain a reliable service. The existing evaluations primarily focus on the resiliency of stored user data, which is insufficient to project the storage service level resiliency. This work proposes an end-to-end resiliency framework for cloud storage services that enables the assessment of the overall resiliency. The framework is based on three properties – service expectations, crucial components for service rendition, and their resiliency to meet the expectations while facing various disruptions. The framework is used to model the resiliency of two distinct and well-known storage services, OpenStack Swift and CephFS, as Stochastic Petri Nets. The models enable the effective quantification of system resiliency through the achieved service reliability.