A simulation study to analyze unreliable file systems with checkpointing and rollback recovery

This paper considers two simulation models for simple unreliable file syste ms with checkpointing and rollback recovery. In Model 1, the checkpoint is generated at a prespecified time and the information on the main memory sin ce the last checkpoint is back-uped in a secondary medium. On the other han d, in Model 2, the checkpointing is executed at the time when the number of transactions completed for processing is achieved at a pre-determined leve l. However, it is difficult to treat such models analytically without emplo ying any approximation method, if queueing effects related with arrival and processing of transactions can not be ignored. We apply the generalized st ochastic Petri net (GSPN) to represent the stochastic behaviour of systems under two checkpointing schemes. Throughout GSPN simulation, we evaluate qu antitatively the maintainability of checkpoint models under consideration a nd examine the dependence of model parameters in the optimal checkpoint pol icies and their associated system availabilities.