Do you have IIS logging enabled? Do you ever use it? If you don’t use it, consider turning it off. By looking at the log files, you can see an awful lot of text is recorded with every visitor. Items such as bytes sent, referrers, and domain/host info slows down the server considerably. Reverse DNS requests when logging host info for a visitor will really slow the server. For small sites hosted on powerful servers performance may not be an issue. If you have a site with many visitors and/or databases (forums), logging can cause significant hard disk activity and paging.
To disable logging, go into the IIS Manager -> Right-click on Websites and select Properties-> Uncheck “Enable Logging”
You can also do this for FTP sites as well. To disable it for a specific site, right-click on the site-name and disable logging.