Long term distributed file reference tracing: implementation and experience

DFSTrace is a system to collect and analyze long-term file reference data in a distributed UNIX workstation environ-ment. The design of DFSTrace is unique in that it pays particular attention to efficiency, extensibility, and the logistics of long-term trace data collection in a distributed environment. The components of DFSTrace are a set of kernel hooks, a kernel buffer mechanism, a data extraction agent, a set of collection servers, and post-processing tools. Our experience with DFSTrace has been highly positive. Tracing has been virtually unnoticeable, degrading perfor-mance 3-7%, depending on the level of detail of tracing. We have collected file reference traces from approximately 30 workstations continuously for over two years. We have implemented a post-processing library to provide a convenient programmer interface to the traces, and have created an on-line database of results from a suite of analysis programs to aid trace selection. Our data has been used for a wide variety of purposes, including file system studies, performance measurement and tuning, and debugging. Extensions of DFSTrace have enabled its use in applications such as field reliability testing and determining disk geometry. This paper presents the design, implementation, and evaluation of DFSTrace an