Understanding Log File Formats
With previous versions of Internet Information Server, each virtual server's activity was contained within a single directory. A new logging architecture was introduced with Internet Information Server 4 that improved performance and allowed for greater flexibility. Now, activity can be separated into distinct directories for each Web site configured on a server.
Although logging provides many benefits, trying to log every access for every service will certainly cause deterioration in performance. Administrators can choose which resources are logged, how often log files are generated, and which files are included in the logging process to limit this effect on performance.
In general, logging FTP or SMTP services ...