Abstract: The workstation file system for the Cedar programming environment was modified to improve its robustness and performance. Previously, the file system used hardware-provided labels on disk blocks to increase robustness against hardware and software errors. The new system does not require hardware disk labels, yet is more robust than the old system. Recovery is rapid after a crash. The performance of operations on file system metadata, e.g., file creation or open, is greatly improved. The new file system has two features that make it atypical. The system uses a log, as do most database systems, to recover metadata about the file system. To gain performance, it uses group commit, a concept derived from high performance database systems. The design of the system used a simple, yet detailed and accurate, analytical model to choose between several design alternatives in order to provide good disk performance. 1.