Upgrading Drupal 6 To Drupal 7 For Large Projects

With Drupal 7 just over a year old everyone is starting to wonder when it's time to upgrade Drupal 6 to 7. Although it will continue to run well for a few more years there are many benefits to Drupal 7 from both the interface and development perspectives. This applies especially to large / on-going projects. If you're managing a site like that, what is your strategy to upgrade?

If you have a lot of plans for future development, chances are that they could benefit from the new APIs in Drupal 7 and the modules which will eventually stop supporting Drupal 6. That makes it likely that you'll need to upgrade eventually. And the longer you wait, the more work you might need to redo. In this case you need the right strategy to start the transition and do it efficiently without halting development on the live version.

On the other hand the Drupal 6 core release will continue to be officially supported until Drupal 8 is released which is well over a year away. Few module developers seem to have abandoned Drupal 6 so far. If it works for you now there isn't an immediate need to switch. Over time as support decreases it will not get as many security updates which may be one of the first concerns. This is already starting to show since Drupal 6 has some bugs on PHP 5.3 and earlier versions of PHP are no longer officially supported.

Given the level of web host and Linux distribution support for older PHP versions and the number of sites on Drupal 6, there may be other developers supporting older versions for some time to come. You can expect it to continue working reliably without major changes. And the Drupal core and major modules rarely have major security issues so they may not need continuous updates (depending on how you use the site).

For more details see our recent guide to upgrading large projects from Drupal 6 to 7.

How are you approaching the upgrade?