Models are gaining importance in software development, for instance in the MDD field, as well as in other disciplines such as biology and physics. Hence, tool support is needed to manage these models and metadata about the models. Model repositories support this trend by managing these model artifacts. While setting up model and metadata repositories, architects have to make several fundamental design decisions and balance various forces. In this paper we describe reusable knowledge in form of reusable architectural decisions for ITarchitects in setting-up, planning, and developing model and metadata repositories, as well as the main decision drivers. Our decisions are documented in a reusable architectural decision model that can be instantiated for a concrete system. It also supports a lightweight approach to architecture documentation. A case study illustrates the decisions made when setting up our own data access object model repository by walking through the reusable architectural...