Is it possible to get rid of content duplicates? I've got a site, mysite.com. Now I'm trying to add blog on it at sub-domain, blog.mysite.com, using the Domain Access module.

When I create an article in blog, with alias blog.mysite.com/article-alias, it is available from main site, by URL mysite.com/article-alias. At the same time, main site articles, like mysite.com/about are available from blog by URL blog.mysite.com/about. No matter which affiliate I'm sending this article to, or which source site I choose, it still happens. Today, I've found that some of such pages were indexed by Google as duplicates, despite having canonical tag.

Is it possible to get rid of such pages with this module settings, or with the help of some additional modules? Still, I can't find no solution.
You can manage your Robots.txt file through Drupal using RobotsTxt module. This way you can exclude whatever content you want from Google, etc.