Upgrading Drupal websites from one major version to the next is painful. Most people solve the problem by sticking with the old version, and I've seen a lot of people give up after trying for many days. I've myself done a good amount of (successful) upgrades from Drupal 5 to Drupal 6 in the past year and decided to share my experience and hopefully help some people get through with it. My presentation Upgrading Drupal takes a look at what issues make those upgrades so damn problematic and what solutions we can implement to solve them. I'll be giving the presentation for the third time at DrupalCamp Spain this coming week-end, and I proposed it as a session for DrupalCon SF (please vote!).
The two main problems with upgrades are complexity and time: a lot of operations need to be performed in a specific order within a short period of time to minimize downtime. Any solution that addresses these two problems will need to be automated, and the best way to do this that I found involved a VCS, drush and some minimal shell scripting. The presentation is about the WHY's, and this article is about the HOW's, with more implementation details that wouldn't fit well in a presentation.
