Scale-out disk storage systems are built using nodes or modules that, when linked together, act as a single system. They allow companies to start small and grow incrementally, adding nodes as they need them, without having to worry about the limits of a single standalone storage system. They offer the advantage of cost-effective manageability, high availability, and reliability. Predictions are that the new wave of scale-out systems could mount a more serious challenge to traditional scale-up systems, now that major vendors are standing behind them. This presentation explores the distinctions between scale-out and scale-up systems, major use cases for this technology and an assessment of new scale-out/clustered storage systems from major vendors.