The question may be imprecise so I will try to explain it in more detail.
For a number of reasons I have lots of copies of the same file on my Linux file-system. Many of them are quite large.
Say I have
/path/to/some.file and copies of this file
/yet/another/path/third.copy. I wonder if there is a file-system which would literally make two of these files act as a reference to the original. Naturally, if user modifies one of them, then and only then they become independent files.
PS. I know this can be (partially) accomplished by using links. But I want this feature I tried to explain above to be transparently handled by the file-system.