I found myself needing to host a number of Drupal sites, all low volume, and having just one system available. Drupal can be configured in the following major ways (there are many others, but these are the common ones): ... Click to read more

  1. Dedicated : One site per system (or virtualized system). This is the bets way to isolate Drupal sites but has a number of performance and resource needs not the least is keeping every system updated and tuned.
  1. VHOST : Multiple sites per system using Apache virtual named hosts (or IP).

The L2 (link2) Drupal module for 4.7 has been upgraded and overhauled for Drupal 6. It is currently in BETA testing.