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 `/other/path/file.name` and `/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.