Performability evaluation of NoSQL-based storage systems

NoSQL database management systems (DBMS) have been commonly adopted in cloud storage applications, as they usually provide better performance and availability than relational DBMSs. Eventual consistency is a remarkable feature of many NoSQL database systems, in which not all redundant nodes have the newest data, but, eventually, such data will be present in all nodes. Distinct consistency levels can be utilized, but they may affect user experience and service level agreements. The assessment of consistency concerning the probability of accessing the newest data is not common, and the jointly evaluation of performance and availability is usually neglected. This work proposes a method based on stochastic Petri nets (SPN) for evaluating the consistency levels of storage systems based on NoSQL DBMS adopting quorum technique. The models take into account distinct consistency levels and redundant nodes for estimating system availability, throughput and the probability of accessing the newest data. Experimental results demonstrate the practical feasibility of our approach.