For this test, I’ve set up a server (1 intel processor/512MB ram/12MB video memory) with Ubuntu Server 10.10 (32 bit).
I could test some static resources but nowadays, particularly all websites are dynamic ones so I’ve installed Mysql/PHP and of course Apache2, all with the default settings, on my server.
Next, I’ve downloaded WordPress and installed it on the server, changed the appearance to ‘pixel theme’ and added a few posts with images in.

Time to test

I’m not going to do fancy stuff, the module is installed with the default options enabled and I’ll just use Firebug to do the tests.

First the tests without the module installed:

The results with the module installed:

Mod_pagespeed_statistics:

Conclusion:

• The amount of requests have been reduced in this case with 2 (-15%)
• The pagesize has been reduced with 5.2KB (-1.5%)
• The loadtime is shorter when mod_pagespeed is enabled (-13%)

The 50% profit claim is a little bit optimistic because the bottleneck in the pageload is the dynamic content and that’s a part where this module doesn’t do anything. But in general, the module does a reasonably good job. I get a 13% profit with mostly default values, a good configured server should propably even do better.
I will definitely test this further and maybe put it one day on a production server.

The config used in this test looks like this:

<IfModule pagespeed_module>
    SetOutputFilter MOD_PAGESPEED_OUTPUT_FILTER
     ModPagespeed on
     ModPagespeedUrlPrefix "http://localhost/"
     ModPagespeedFileCachePath "/var/mod_pagespeed/cache/"
     ModPagespeedGeneratedFilePrefix "/var/mod_pagespeed/files/"
     ModPagespeedRewriteLevel CoreFilters
     ModPagespeedDomain localhost
     ModPagespeedEnableFilters add_instrumentation
<IfModule>

My full configuration file can be downloaded here.

In most of the cases, there is more than just one website on a server.
Though, it is very important that you can measure the stats of all the websites separately.
I’ll tell you in a few lines how you can achieve this with webalizer.

This tutorial is tested with Webalizer on Ubunty but I presume it will work almost the same way in other distros.

First of all you have to install webalizer on your system.

sudo apt-get install webalizer

After installation of webalizer, the configurationfiles are per default stored in /etc/webalizer.
Move to that directory and make a copy of the config-file.

sudo cp webalizer.conf MySiteName.conf

When the copy is created you have to open it in your favorite editor (I use vim)

sudo vim MySiteName.conf

Scroll down till you find the LogFileattribute and change it to the accesslogfile of MySiteName.
You also have to tell the script where the outputfiles will be stored. This is normally a place which is accessible by the browser.

LogFile /www/mysite/logs/access.log
OutputDir /www/mysite/public_html/webalizer

These are the only 2 parameters which you have to change. You can scroll through the rest of the file and make changes towards your preferences.

All is done now so you can run webalizer with the new configuration file

webalizer -c /etc/webalizer/MySiteName.conf

Webalizer will run and should be accessible through your webbrowser.
Obviously, it would kinda suck if you have to run the webalizerscript every time you want to see the stats so we gonna make a cron which will run the script every hour

crontab -e

And fill in:

0 * * * * webalizer -c /etc/webalizer/MySiteName.conf

Voila, all done