The log files generated while operating a file system in disconnected mode grow to substantial sizes. Eliminating redundant or useless operations in these logs can free up scarce disk space on laptops, reduce replay times, and reduce the frequency of data conflict. Our approach uses a rule-based portable peephole optimizer for compilers. This suggests a general method of optimization for any system that performs logging at the vnode layer. 1. Introduction One goal of mobile computing is to provide users with a system that faithfully emulates the desktop environment. The mobile environment makes this goal a difficult one to reach because of limitations such as sporadic, low-bandwidth networks. Moreover, mobile computers tend to be resource poor, so that consumption of resources, such as disk space, demands careful control. The conventional paradigm for modern computing systems is distributed computing. An essential service in a distributed computing environment is the (distributed) fil...