Lessons from FTM: an experiment in design and implementation of a low-cost fault tolerant system

This paper describes an experiment in the design of a general purpose fault tolerant system, FTM. The main objective of the FTM design was to implement a low-cost fault-tolerant system that could be used on standard workstations. At the operating system level, the authors' goal was to offer fault-tolerance transparency to user applications. In other words, porting an application to FTM need only require compiling the source code without having to modify it. These objectives were achieved using the Mach micro-kernel and a modular set of reliable servers which implement application checkpoints and provide continuous system functions despite machine crashes. At the architectural level, their approach relies on a high-performance stable storage implementation, called stable transactional memory (STM), which can be implemented either by hardware or software. The authors first motivate their design choices, then detail the FTM implementation at both architectural and operating system level. They discuss the reasons for the evolution of their stable memory technology from hardware to software. They evaluate the performance of the FTM prototype. They conclude with lessons learned and give some assessments.