The architecture is the fundamental framework for designing and implementing large scale software, and the ability to trace and control its evolution is essential. However, many traditional software configuration management tools view `software' merely as a set of files, not as an architecture. This introduces an unfortunate impedance mismatch between the design domain (architecture level) and configuration management domain (file level.) This paper presents a software configuration management model that allows tight version control and configuration management of the architecture of a software system. Essential features of the model have been implemented in a research prototype, Ragnarok. Two years of experience using Ragnarok in three, real, small- to medium sized, projects is reported. The conclusion is that the presented model is viable, feels `natural' for developers, and provides good support for handling an evolving architecture.