We developed two workload generators: wg-Squid which mimics Squid's interaction with the file system, and wg-Hummingbird which issues Hummingbird calls. The same wg-squid workload generator was used with the various UFS implementation, EFS and XFS. The generators take as input the modified proxy access log. The workload generators operate in a trace-driven loop which processes logged events sequentially without pause2. This simulates a heavily loaded server.