FreeBSD is the system of choice for high performance network applications. FreeBSD will outperform other systems when running on equivalent hardware. The largest and busiest public server on the Internet, at ftp.freesoftware.com, uses FreeBSD to serve more than 1.2TB/day of downloads. FreeBSD is used by Yahoo!, Qwest and many others as their main server OS because of its ability to handle heavy network traffic with high performance and rock solid reliability. Linux performs well for most applications, however the performance is not optimal under heavy network load. The network performance of Linux is 20-30% below the capacity of FreeBSD running on the same hardware 2. The situation has improved somewhat recently and the 2.4 release of the Linux kernel will introduce a new virutual memory system based on the same concepts as the FreeBSD VM system. Since both operating systems are open source, beneficial technologies are shared and for this reason the performance of Linux and FreeBSD is rapidly converging. Windows is adequate for routine desktop apps, but it is unable to handle heavy network loads. A few organizations try to make it work as an Internet server. For instance, barnesandnoble.com uses Windows-NT, as can be verifyed by the error messages that their webserver produces, such as this recent example: Error Message: [Microsoft][ODBC SQL Server Driver][SQL Server]Can't allocate space for object 'queryHistory' in database 'web' because the 'default' segment is full.
For their own "Hotmail" Internet servers, Microsoft used FreeBSD for many years.