The impact of logging Internet Information Server (IIS) activity to disk is minimal compared to logging it to a SQL Server database. The performance impact of logging to SQL Server is greater and depends on the SQL Server implementation and the hardware you use. See your SQL Server documentation for more information on increasing performance.

If disk logging is used, data is cached in 64K chunks. When the server has 64K of log data cached, it writes the data to disk.

NOTE: Stopping the WWW, FTP, or Gopher service forces the cached data to be written to the log file. If SQL Server logging is used, the log is always up to date because SQL Server entries are written immediately.

You may experience problems implementing live reports when using these files as the data source for two reasons:

•	The current log file is held open until it reaches the maximum size or time interval specified in the Internet Server Manager. The log file closes when the next log entry is written after midnight of the day the log file time limit expires.
•	The log file is updated in 64K chunks. On servers that do not have a high usage rate, the statistics will not be up-to-date because of the delayed write.