Software fault tolerance mechanisms aim at improving the reliability of software systems. Their effectiveness (i.e., reliability impact) is highly application-specific and depends on the overall system architecture and usage profile. When examining multiple architecture configurations, such as in software product lines, it is a complex and error-prone task to include fault tolerance mechanisms effectively. Existing approaches for reliability analysis of software architectures either do not support modelling fault tolerance mechanisms or are not designed for an efficient evaluation of multiple architecture variants. We present a novel approach to analyse the effect of software fault tolerance mechanisms in varying architecture configurations. We have validated the approach in multiple case studies, including a large-scale industrial system, demonstrating its ability to support architecture design, and its robustness against imprecise input data.