How does DrupalGardens.com setup a new website? How does drupalgardens.com creates a new website?


It creates a separate directory for Drupal, containing all core files(modules, themes, includes, ...)


OR


It shares the themes, modules and core files, and just creates a sub-site in drupalgardens.com


The second one is more reasonable, But When I read the source HTML I saw the following line:

&lt;link type="text/css" rel="stylesheet" href="http://[mysitename].drupalgardens.com/modules/acquia/gardens_client/gardens_alert.css?lva62a" media="all" /&gt;

That, in my opinion, says that my website is outside of drupalgardens and has a separate directory instead of being a sub-site in drupalgardens.com
Yes, Drupal Gardens sites are multisites. Modules inside either /modules or /sites/all/modules are shared by all sites in a multisite installation. If we installed an entire instance of Drupal for each individual Gardens site it would be a serious waste of disk space.