I just decided to play a little with Netcraft's What's that site running? and uptime tracking service. Here are a few of the things I noticed...

Of the more popular search engines (Google, Yahoo!, MSN, AlltheWeb, Lycos, and Ask Jeeves), they all run Unix systems (specifically, Linux or FreeBSD) except for MSN and Lycos, which use some form of Windows. Those that use Unix systems all have at least double the average uptime of those that use Windows system, and most have triple the uptime.

The Windows servers that run the Microsoft homepage have had to be restarted every month this year, whereas the FreeBSD servers that run Yahoo! have currently been up for an average of three months. According to Netcraft, Microsoft.com's current longest-running server has been up for almost 80 days, while Yahoo!'s current longest-running server has been up for about 270 days.

Unfortunately, Netcraft doesn't provide information about Google's uptime, but it does show that they're using their custom-built Unix-based web servers. It uses two versions: GWS/2.1 and GFE/1.3 (which I think stands for Google Front End). About half of them run on Linux and the other half run on an unrecognized operating system. Clicking on Google Inc brings you to a list of Google domains with some information about each. It appears as though GFE/1.3 runs Google Answers and the Google API sections of the site, NFE/0.31 runs Google News, and DFE/1.0 runs Google Directory. Apache is also used to run a few sections of Google.

It could all be apache, with a CGI script sending a different server header. this is very easy to do with php for example.
<?php
Header('Server: GFE/1.3');
Header('Content-type: text/html');
readfile('thispagecontent.htm');
?&rt;

And let apache take care of the rest :P

Or it could simple be apache httpd customization, and modification of the version. Google has a lot of internal
research going on, and they seem to be
working quite deeply on OS internals!
(a good example being their fs, http://labs.google.com/papers/gfs.html)

Header('Server: GFE/1.3');

It doesnt't work... You have to customize source files to do that...

You don't have to modify any headers to send modified headers.. BTW, that's PHP.

giannoug,
www.giannou.net