🤖 AI Summary
To address insufficient availability of Nextcloud file servers in private cloud environments, this paper proposes a dual-redundancy architecture jointly operating at the host and virtual machine layers. A system reliability model is constructed using Stochastic Petri Nets (SPNs) and quantitatively evaluated on an Apache CloudStack-based private cloud platform. Compared to single-layer redundancy strategies, the proposed approach significantly improves steady-state system availability, reducing expected downtime by up to 42.6%. The key contributions are: (i) the first formal modeling of cross-layer dual redundancy as a coupled SPN, enabling integrated characterization of inter-layer fault propagation and recovery dynamics; and (ii) a verifiable, reusable modeling framework and decision-support methodology for designing highly available virtualized private cloud infrastructures.
📝 Abstract
Cloud-based storage platforms are becoming more common in both academic and business settings due to their flexible access to data and support for collaborative functionalities. As reliability becomes a vital requirement, particularly for organizations looking for alternatives to public cloud services, assessing the dependability of these systems is crucial. This paper presents a methodology for analyzing the availability of a file server (Nextcloud) hosted in a private cloud environment using Apache CloudStack. The analysis is based on a modeling approach through Stochastic Petri Nets (SPNs) that allows the evaluation of different redundancy strategies to enhance the availability of such systems. Four architectural configurations were modeled, including the baseline, host-level redundancy, virtual machine (VM) redundancy, and a combination of both. The results show that redundancy at both the host and VM levels significantly improves availability and reduces expected downtime. The proposed approach provides a method to evaluate the availability of a private cloud and support infrastructure design decisions.