Abstract: A method and apparatus for determining the size of a file cache for storing data is described. The method includes activating a filesystem logging mechanism to monitor filesystem transactions performed on the computer by the user. Next, a file cache is provided under computer control for storing at least a portion of at least one computer file. Also, a filesystem log file is provided for storing records of filesystem transactions invoked by the computer. A user work cycle is then performed during which the filesystem logging mechanism monitors filesystem transactions invoked by the computer and stores records of certain filesystem transactions to the filesystem log file. Finally, the size of the file cache required to store the information cached during the work cycle is determined by processing the log file. Also provided is a computer program product having computer readable code for determining the size of a file cache.