How SVN store branch on the server?

Question

I am trying to understand how Subversion stores branch code on the server side. Does it stores a diff of source based on commit id or replicate a source code in the branch?

Answer 1

SVNBook | Using Branches tells us (check the "Cheap Copies" part):

Subversion's repository has a special design. When you copy a directory, you don't need to worry about the repository growing huge—Subversion doesn't actually duplicate any data. Instead, it creates a new directory entry that points to an existing tree. If you're an experienced Unix user, you'll recognize this as the same concept behind a hard link. As further changes are made to files and directories beneath the copied directory, Subversion continues to employ this hard link concept where it can. It duplicates data only when it is necessary to disambiguate different versions of objects.

You may find SVNBook very helpful.