Can anyone explain to me what Embedded Repository means?
Is it also possible to have one alfresco installation with multiple repositories independant of each other.
This meaning, that if i were to store file a in repository a, that this file cannot be stored in repository b because it is already in repository a.
Embedded typically mean you include the repository in something else. Sort of like you can have a software product that has a database inside it, that's an embedded database.
Please let me know if you are thinking about it in a different context.
One Alfresco installation with multiple repositories - yes - this is what mult-tenancy features that I believe are currently in HEAD are all about. Idea to run multiple repositories independent of each other.
As far as checking if a file stored in A cannot be stored in B, you can do that programatically by file comparison, but Alfresco does not do that for you.