Drupal performance: separate sites vs multisite configuration on single host?

Does anyone have performance data on running several separate Drupal sites (on a single host) vs using Drupal's multisite configuration?

I face a choice: configure several Apache virtual hosts with completely separate codebases, vs a shared multisite instance of Drupal core with site directories sites/www.example.com, sites/www.example1.com, etc. [In a multisite configuration, there are still Apache virtual hosts, but the all of their DocumentRoot entries point to the multisite Drupal directory.] I assume the multisite method uses Drupal code to perform virtual host dispatching, which I imagine is slower than letting Apache do it. On the other hand, I assu开发者_如何转开发me there is a probably a caching benefit to the multisite configuration.

Performance comparison data anyone?

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keith,

if you have a single site setup, chances are you have it under /sites/default. from the documentation on settings.php, we see that drupal looks for the settings.php in 9 places before it defaults to the sites/default/settings.php, as per the snippet below:

 * The configuration directory will be discovered by stripping the
 * website's hostname from left to right and pathname from right to
 * left. The first configuration file found will be used and any
 * others will be ignored. If no other configuration file is found
 * then the default configuration file at 'sites/default' will be used.
 *
 * For example, for a fictitious site installed at
 * http://www.drupal.org/mysite/test/, the 'settings.php'
 * is searched in the following directories:
 *
 *  1. sites/www.drupal.org.mysite.test
 *  2. sites/drupal.org.mysite.test
 *  3. sites/org.mysite.test
 *
 *  4. sites/www.drupal.org.mysite
 *  5. sites/drupal.org.mysite
 *  6. sites/org.mysite
 *
 *  7. sites/www.drupal.org
 *  8. sites/drupal.org
 *  9. sites/org
 *
 * 10. sites/default

adding another single site setup will still keep those 9 checks and will add the apache virtual on top of it, so i don't see how that can possibly be any faster.

additionally, if you end up with a lot of sites to manage, having several instances of drupal unnecessarily increases your administration overhead. If you plan to have a lot of drupal sites, i would recommend you look at the hosting project, which is part of the aegir hosting system. the guys maintaining that project put a lot of effort to simply the maintenance and deployment of large number of drupal sites.