Building one Drupal site is a fair amount of work in and of itself. But what about working with multiple Drupal sites? Sometimes you have a few sites that make sense together, either from a maintenance perspective, or due to an overlap in content or users. There are a number of different ways to approach this in Drupal, and which path you follow varies considerably depending on the exact use case you need to fulfill. In this lesson we'll get a good look at the problem multiple sites can pose, and list out some common use cases. Then we'll take a look at three different broad categories of solutions, with some specific architectural approaches. The rest of this series will walk through managing multiple sites using Drupal core's built-in multisite system.
If you are interested in working with the Domain Access project instead of core multisite, you should look at the Introduction to Domain Access series.