Sessions: A technique and its application to the UNIX file system

This paper describes a new technique for analyzing dynamic file usage patterns based upon classification of file sessions. Afire session Is defined to be the set of operations on a given file from the moment it is opened until the moment it is closed. If file system measurement data is organized into sessions, each session may then be classified by the pattern of file use that it demonstrates. Examination of the overall pattern of file use revealed by this classification leads to valuable insights for file system designers. The technique is Illustrated by applying it to data collected from a UNIX^® file system by John Ousterhout at Berkeley [6]. One surprising result was a high incidence of “lock files”.