Indexing in multilingual sites
There are 2 ways of correct linking system to separate multilingual sites.
- Wikipedia (http://en.site.com http://ru.site.com http://uk.site.com), where pages that are identical in content but different in language are separated into separate subdomains.
- Microsoft (http://site.com/en http://site.com/ru http://site.com/uk), where pages that are identical in content but different in language are divided into separate subcategories.
Wikipedia or subdomain system
With a subdomain system, there is an accelerated indexing, as well as the possibility of arranging geography for the site's subdomains.
This scheme is more suitable for an information resource that can promote itself independently as an information environment with unique content.
Microsoft or subdirector
With a subdirectory system, slow indexing occurs, problematic arrangement of the site geography for promotion is set manually, possible problems in issuing in different countries.
In fact, the problem of indexing for another country is not necessarily problematic. This version is better suited for service sites (the exception, again, is huge sites like eBay, in which, due to too large an audience, the creators simply have to scatter everything on different domains and machines in different parts of the globe, attaching it to their affiliates to provide better performance with users).
Theoretically, the problem for promotion is completely solvable - turn the name /EN/ as a key one. Again, you will have to spend almost the same amount of resources on promotion as in 1 case. After all, different search engines (of course there are exceptions), different languages, different processing of weight, ratings, and so on and so forth ...
Conclusion:
The subdomain system is most convenient for all types of sites. Sub-directory is best used on SERPs for one country/region, providing a language alternative.