Our digital society’s ever-increasing demand for data storage has driven up costs and security concerns, particularly with the shift towards outsourced third-party storage providers. This transition raises critical issues regarding privacy, trust, and data availability, i.e. the assurance that stored data remains accessible and retrievable. This paper introduces a novel model that abstracts data-storage mechanisms by identifying distinct entities, each with a specific role in managing the data flow. Our model is designed to describe storage mechanisms, ranging from centralized to fully-decentralized systems, together with some data availability guarantees. We highlight the underlying trust assumptions, providing a guideline for understanding application requirements and systematizing knowledge on data storage and availability. To illustrate our model usefulness, we examine several real-world data-storage-and-availability solutions, classifying them within our model as well as showcasing advantages and disadvantages. We conclude by comparing these solutions, which lets us propose open questions and future research directions for data-storage-and-availability methodologies.