Hello to all,
Sorry if this is a long post! Spent days searching on forums and handbooks, both with drupal's search feature and using google.
I've been having very bad nightmares recently with my site and after several 16 hour workdays, a migration from a shared hosting environment to a dedicated server and upgrading of all software packages on the server side to their latest versions. The only thing that has not the latest release installed is mysql.
We're using drupal 4.6.6 with mysql 4.1 and php 4.4.2 on a site with approx 300 taxonomy terms, 5 vocabularies and about 2000 nodes so far. It might be one of the modules I was using, since the site was originally implemented using 4.6.3 and then upgraded to the next versions.
What seems to be lagging is the mysql server. The site is hosted on a dedicated server, along with some other drupal sites which use minimal resources (seperate installations). The server runs on Redhat enterprise 3 and is manageable via a plesk control panel. I haven't got enough experience to ssh into the server and alter the mysql configuration, but my hosting's support is helpful and can make any alterations required.
The homepage has proven to be one of the heaviest pages. It runs one query and prints the 30 latest results it finds from the node table. Also all categories and nodes have an automatic path created for them through pathauto. There was an isssue about the pathauto module slowing the server and I installed a patched version which was supposed to fix that in 4.6.6.