Caching is a big, big topic if a website is successful. One reason why Drupal is so popular is the way of caching.
- all pages for anomynous users get cached
- The menu system gets build and cached for every user
- The siteconfiguration $conf
- Content which get filtered (f.e. BB Code)
Three functions are important
A few Table are interesting
- cache_...
Cached data is saved as string, arrays and objects needs to be serialized (In Drupal 6 this will happen behind the themes)
Now he shows what caching means.
Page caching:
He uses the devel Module to generate a lot of data and plys with the cache. The db queries went down from 181 queries to 138 queries. For anonymous users chaching reduces from 134 queries to 10 queries!
Drupal has normal and aggressive caching.
Another possibility is the Memcache module
It stores things in the computers memory. Its the fastest possibility for chaching! To use the module it is necessary to change your settings.php file.
$conf = array(
'cache_inc' => './sites/all/modules/memcache/memcache.inc',
);
Redundant Cache
It is possible to share a cache between different machines
What do I need on my machine?
You need to install Memcached and the PECL Memcache library to get it worked.
Look at the advanced cache module. It doesn't needs memcache. It's a different approach.
Zofingen, Switzerland, Previon AG
Nürnberg, Germany
Kirchberg, Switzerland, joomlanews.ch 
