Building storage systems has remained the domain of systems experts for many years. They are complex and difficult to implement. Extreme care is needed to ensure necessary guarantees of performance and operational correctness. Furthermore, because of restrictions imposed by kernel-based designs, many legacy implementations have traded software flexibility for performance. Their implementation is restricted to compiled languages such as C and assembler, and reuse tends to be difficult or constrained. Nevertheless, storage systems are implicitly well-suited to software reuse and compositional software construction. There are many logical functions, such as block allocation, caching, partitioning, metadata management and so forth, that are common across most variants of storage. In this paper, we present Comanche, an open-source project that considers, as first-class concerns, both compositional design and reuse, and the need for high-performance.